System and method for measuring and treating a liquid stream

ABSTRACT

A method and system of treating a liquid stream is provided. The water is treated by utilizing a free radical scavenging system and a free radical removal system. The free radical scavenging system can utilize actinic radiation with a free radical precursor compound, such as ammonium persulfate. The free radical removal system can comprise use of a reducing agent. The water may be further treated by utilizing ion exchange media and degasification apparatus. A control system may be utilized to measure and regulate addition of the precursor compound, the intensity of the actinic radiation, and addition of the reducing agent to the water.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation-in-part application of co-pendingU.S. patent application Ser. No. 13/007,946, titled “SYSTEM FORCONTROLLING INTRODUCTION OF A REDUCING AGENT TO A LIQUID STREAM,” filedJan. 17, 2011, which is a continuation-in-part application of U.S.patent application Ser. No. 12/013,127, titled “METHOD AND SYSTEM FORPROVIDING ULTRAPURE WATER,” filed Jan. 11, 2008, which is a continuationapplication of U.S. patent application Ser. No. 11/872,625, titled“METHOD AND SYSTEM FOR PROVIDING ULTRAPURE WATER,” filed on Oct. 15,2007, which claims the benefit of U.S. Provisional Application No.60/909,795, filed Apr. 3, 2007, titled “POINT OF USE ULTRA PURE WATERSKID WITH ADVANCED OXIDATION PROCESS,” each of which is incorporatedherein by reference in its entirety for all purposes.

BACKGROUND OF INVENTION

1. Field of Invention

This disclosure relates to systems and methods of treating a liquidstream and, in particular, to systems and methods of reducing ormaintaining a contaminant level of a liquid stream.

2. Discussion of Related Art

Ejzak, in U.S. Pat. No. 4,277,438, discloses a method and apparatusmeasuring the amount of carbon and other organics in an aqueoussolution. A multistage reactor that employs ultraviolet radiation isused to promote oxidation of a test sample. Oxygen and an oxidizingagent such as sodium persulfate are introduced into the solution priorto irradiation.

Martin, in U.S. Pat. No. 6,991,735, discloses a free radical generatorand method of sanitizing water systems.

SUMMARY OF THE INVENTION

One or more aspects of the disclosure provide for a water treatmentsystem. The system comprises an oxidizing agent concentration sensorcomprising an oxidizing agent conductivity cell, the oxidizing agentconcentration sensor in fluid communication with a liquid stream. Thesystem comprises a source of reducing agent disposed to introduce thereducing agent to the liquid stream downstream of the oxidizing agentconcentration sensor. The system comprises a reducing agentconcentration sensor comprising a reducing agent conductivity cell, thereducing agent concentration sensor in fluid communication with theliquid stream and located downstream of the source of reducing agent.The system comprises a controller configured to generate a controlsignal that regulates at least one of a rate of addition and an amountof the reducing agent introduced into the liquid stream based on atleast one input signal from one of the oxidizing agent concentrationsensor and the reducing agent concentration sensor.

The oxidizing agent concentration sensor may further comprise a firstsource of ultraviolet light. The reducing agent concentration sensor mayfurther comprise a second source of ultraviolet light. The system mayfurther comprise a source of ultraviolet light configured to provideultraviolet light to the first sensor and the second sensor. Theoxidizing agent may be persulfate. The reducing agent may be sulfurdioxide. The controller may be further configured to generate thecontrol signal based on at least one of a first input signal from theoxidizing agent conductivity cell prior to irradiation from the firstsource of ultraviolet light and a second input signal from the oxidizingagent conductivity cell subsequent to irradiation from the first sourceof ultraviolet light. The controller may be further configured togenerate the control signal based on at least one of a third inputsignal from the reducing agent conductivity cell prior to irradiationfrom the second source of ultraviolet light and a fourth input signalfrom the reducing agent conductivity cell subsequent to irradiation fromthe second source of ultraviolet light. The system may further comprisean actinic radiation reactor located upstream of the oxidizing agentconcentration sensor.

The system may further comprise a source of persulfate precursorcompound disposed to introduce at least one persulfate precursorcompound into the actinic radiation reactor. The system may furthercomprise a total organic carbon concentration sensor located upstream ofthe actinic radiation reactor. The liquid stream upstream of theoxidizing agent concentration sensor may have a total organic carbonvalue of less than 25 ppb. The liquid stream upstream of the oxidizingagent concentration sensor may have a resistivity of at least about 1megaohm-cm. The liquid stream upstream of the oxidizing agentconcentration sensor may have a resistivity of at least about 5megaohm-cm. The liquid stream upstream of the oxidizing agentconcentration sensor may have a resistivity of at least about 10megaohm-cm. The liquid stream upstream of the oxidizing agentconcentration sensor may have a resistivity of at least about 15megaohm-cm.

One or more aspects of the disclosure provide for a method forcontrolling introduction of a reducing agent to a liquid streamcomprising: measuring a first conductivity of the liquid stream in afirst conductivity cell. The method further comprises irradiating theliquid stream to provide an irradiated liquid stream. The method furthercomprises measuring a second conductivity of the irradiated liquidstream in the first conductivity cell. The method further comprisescalculating the oxidizing agent concentration of the liquid stream basedin part on the first conductivity measurement and the secondconductivity measurement. The method further comprises introducing areducing agent to the liquid stream to provide a reduced liquid stream.The method further comprises measuring a third conductivity of thereduced liquid stream in a second conductivity cell. The method furthercomprises irradiating the reduced liquid stream to provide an irradiatedreduced liquid stream. The method further comprises measuring a fourthconductivity of the irradiated reduced liquid stream in the secondconductivity cell. The method further comprises calculating the reducingagent concentration based in part on the third conductivity measurementand the fourth conductivity measurement. The method further comprisesregulating at least one of a rate of addition and an amount of thereducing agent introduced to the liquid stream based in part on thecalculated oxidizing agent concentration and the calculated reducingagent concentration.

The oxidizing agent may comprise persulfate. The reducing agent maycomprise sulfur dioxide. The liquid stream upstream of the oxidizingagent concentration sensor may have a resistivity of at least about 1megaohm-cm. The liquid stream upstream of the oxidizing agentconcentration sensor may have a resistivity of at least about 5megaohm-cm. The liquid stream upstream of the oxidizing agentconcentration sensor may have a resistivity of at least about 10megaohm-cm. The liquid stream may have a resistivity of at least about15 megaohm-cm.

One or more aspects of the disclosure provide for a method for measuringan oxidizing agent concentration and a reducing agent concentration in aliquid stream having a resistivity of at least about 15 megaohm-cm. Themethod comprises measuring a first conductivity of the liquid stream ina first conductivity cell. The method comprises irradiating the liquidstream to provide an irradiated liquid stream. The method comprisesmeasuring a second conductivity of the irradiated liquid stream in thefirst conductivity cell. The method comprises calculating the oxidizingagent concentration of the liquid stream based in part on the firstconductivity measurement and the second conductivity measurement. Themethod comprises introducing a reducing agent to the liquid stream toprovide a reduced liquid stream. The method comprises measuring a thirdconductivity of the reduced liquid stream in a second conductivity cell.The method comprises irradiating the second portion of the reducedliquid stream to provide an irradiated reduced liquid stream. The methodcomprises measuring a fourth conductivity of the irradiated reducedliquid stream in the second conductivity cell. The method comprisescalculating the reducing agent concentration of the reduced liquidstream based in part on the third conductivity measurement and thefourth conductivity measurement. The oxidizing agent may comprisepersulfate. The reducing agent may comprise sulfur dioxide.

One or more aspects of the disclosure provide for a water treatmentsystem. The system may comprise a source of reducing agent. The systemmay comprise a controller configured to generate a control signal thatregulates introduction of reducing agent from the source of reducingagent into a liquid stream to provide a reduced liquid stream. Thesystem may comprise a concentration sensor comprising a conductivitycell, the concentration sensor configured to receive a portion of theliquid stream and to measure an oxidizing agent concentration of theportion of the liquid stream, the concentration sensor furtherconfigured to receive a portion of the reduced liquid stream and tomeasure a reducing agent concentration of the portion of the reducedliquid stream, wherein the control signal is based in part on an inputsignal from the concentration sensor.

The concentration sensor may further comprise a source of ultravioletlight to provide irradiation to the conductivity cell. The oxidizingagent concentration may be persulfate concentration. The reducing agentmay be sulfur dioxide. The input signal may comprise a first inputsignal from the conductivity cell prior to irradiation of the portion ofthe liquid stream, and a second input signal from the conductivity cellsubsequent to irradiation of the portion of the liquid stream. The inputsignal may further comprise a third input signal from the conductivitycell prior to irradiation of the portion of the reduced liquid stream,and a fourth input signal from the conductivity cell subsequent toirradiation of the portion of the reduced liquid stream. The system mayfurther comprise an actinic radiation reactor located upstream ofintroduction of the reducing agent into the liquid stream. The systemmay further comprise a source of persulfate precursor compound disposedto introduce at least one persulfate precursor compound into the actinicradiation reactor. The system may further comprise a total organiccarbon concentration sensor located upstream of the actinic radiationreactor. The liquid stream downstream of the actinic radiation reactormay have a total organic carbon value of less than 25 ppb. The liquidstream downstream of the actinic radiation reactor may have aresistivity of at least about 1 megaohm-cm. The liquid stream downstreamof the actinic radiation reactor may have a resistivity of at leastabout 5 megaohm-cm. The liquid stream downstream of the actinicradiation reactor may have a resistivity of at least about 10megaohm-cm. The liquid stream downstream of the actinic radiationreactor may have a resistivity of at least about 15 megaohm-cm.

One or more aspects of the disclosure provide for a method forcontrolling introduction of a reducing agent to a liquid streamcomprising. The method comprises introducing a portion of the liquidstream to a concentration sensor comprising a conductivity cell. Themethod comprises measuring a conductivity of the portion of the liquidstream in the conductivity cell. The method comprises irradiating theportion of the liquid stream to provide an irradiated liquid stream;measuring a conductivity of the irradiated liquid stream in theconductivity cell. The method comprises calculating an oxidizing agentconcentration of the liquid stream based in part on the conductivity ofthe portion of the liquid stream and the conductivity of the irradiatedliquid stream. The method comprises introducing a reducing agent to theliquid stream to provide a reduced liquid stream. The method comprisesintroducing a portion of the reduced liquid stream to the concentrationsensor. The method comprises measuring a conductivity of the portion ofthe reduced liquid stream in the conductivity cell. The method comprisesirradiating the portion of the reduced liquid stream to provide anirradiated reduced liquid stream. The method comprises measuring aconductivity of the irradiated liquid stream in the conductivity cell.The method comprises calculating a reducing agent concentration of thereduced liquid stream based in part on the conductivity of the portionof the reduced liquid stream and the conductivity of the irradiatedreduced liquid stream. The method comprises regulating introduction ofthe reducing agent to the liquid stream based in part on the oxidizingagent concentration and the reducing agent concentration. The oxidizingagent may comprise persulfate. The reducing agent may comprise sulfurdioxide. The liquid stream may have a resistivity of at least about 1megaohm-cm. The liquid stream may have a resistivity of at least about 5megaohm-cm. The liquid stream may have a resistivity of at least about10 megaohm-cm. The liquid stream may have a resistivity of at leastabout 15 megaohm-cm.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are not intended to be drawn to scale. In thedrawings, each identical or nearly identical component that isillustrated in various figures is represented by a like numeral. Forpurposes of clarity, not every component may be labeled in everydrawing.

In the drawings:

FIG. 1 is a schematic drawing illustrating a system in accordance withone or more embodiments of the invention;

FIG. 2 is a schematic drawing illustrating a system in accordance withone or more embodiments of the invention;

FIG. 3 is a schematic drawing illustrating a vessel in accordance withone or more embodiments of the invention;

FIG. 4A is a schematic drawing illustrating a vessel in accordance withone or more embodiments of the invention;

FIG. 4B is a schematic drawing illustrating a vessel in accordance withone or more embodiments of the invention;

FIG. 5 is a schematic drawing illustrating a sensor and controllersystem in accordance with one or more embodiments of the invention;

FIG. 6 is a schematic drawing illustrating a processor or control systemupon which one or more embodiments of the invention may be practiced;

FIG. 7 is a graph showing the water quality of the ultrapure waterproduct in accordance with some embodiments of the invention;

FIG. 8 is a graph showing a relationship between total organic carbon(TOC) concentration and time in accordance with one or more embodimentsof the invention;

FIG. 9 is a graph showing a relationship between total organic carbon(TOC) concentration and time in accordance with one or more embodimentsof the invention;

FIG. 10 is a graph showing a relationship between total organic carbon(TOC) concentration and time in accordance with one or more embodimentsof the invention;

FIG. 11 is a graph showing a relationship between total organic carbon(TOC) concentration and time in accordance with one or more embodimentsof the invention;

FIG. 12 is a graph showing a relationship between residual persulfateand time in accordance with one or more embodiments of the invention;and

FIG. 13 is a graph showing a relationship between sulfur dioxideconcentration and change in conductivity in accordance with one or moreembodiments of the invention;

FIG. 14 is a schematic drawing illustrating a sensor and controllersystem in accordance with one or more embodiments of the invention;

FIG. 15 is a schematic drawing illustrating a sensor and controllersystem in accordance with one or more embodiments of the invention;

FIG. 16 is a graph showing conductivity measurements in accordance withone or more embodiments of the invention in which the oxidizing agentconcentration sensor comprises two conductivity cells;

FIG. 17 is a graph showing conductivity measurements in accordance withone or more embodiments of the invention; and

FIG. 18 is a graph showing conductivity measurements in accordance withone or more embodiments of the invention in which the oxidizing agentconcentration sensor comprises one conductivity cell.

DETAILED DESCRIPTION

One or more aspects of the invention can be directed to water treatmentor purification systems and techniques. The various systems andtechniques of the invention typically utilize or comprise one or moreunit operations that remove undesirable species from a process fluid orstream. A plurality of unit operations may be utilized serially or inparallel flow arrangement, or a combination of serial and parallel flowarrangement, to facilitate non-selective or selective removal or areduction of concentration or level of a variety of target species orcompounds, which are typically undesirable or objectionable, in aprocess stream. Further, the systems and techniques of the invention mayutilize one or more unit operations to facilitate adjustment of aconcentration of a species or a byproduct species generated from a unitoperation of the system. Some aspects of the invention can be directedto techniques and systems or components thereof that treat or purifywater that, in some cases, can be characterized as having a low level ofimpurities or contaminants. Some advantageous aspects of the inventioncan be directed to systems and techniques that provide ultrapure water.Particularly advantageous aspects of the invention can be directed tosystems and techniques that provide ultrapure water for use insemiconductor processing or fabrication operations. For purposes of thisdisclosure ultrapure water may be understood as water having either atotal organic carbon value of less than 25 ppb or a resistivity of atleast about 15 megaohm-cm. In certain embodiments, ultrapure water mayhave a resistivity of at least about 18 megaohm-cm.

In some cases, the invention provides systems and techniques thatprovide make-up water in a circulating water or ultrapure water systemin a manner that maintains a water or ultrapure water characteristic ofthe water circuit containing water or ultrapure water. The systems andtechniques of the invention may, in some cases, co-mingle make-up orinlet water or ultrapure water with treated water or ultrapure water.Still further aspects of the invention can be directed to controlsystems and techniques suitable for use with water treatment orpurification systems. Even further aspects of the invention can bedirected to control systems and techniques that facilitate semiconductorfabrication operations by providing ultrapure water. Indeed, someaspects of the invention may be directed to control systems andtechniques that facilitate water or ultrapure water treatment orpurification by utilizing a feedforward or a feedback approach or both.Even further aspects of the invention can be directed to techniques formeasuring a level or concentration of a target species or compound inthe water or ultrapure water or a liquid stream. The measuringtechniques may utilize control systems and techniques that facilitateproviding ultrapure water.

In accordance with at least one aspect of the invention, someembodiments thereof can involve a system for treating water. The systemand techniques of the invention can involve a first process train thatrelies on utilizing purified water to create conditions that areconducive to free radical scavenging along with one or more ancillaryprocess trains with unit operations that remove or at least reduce theconcentration of byproducts of upstream processes. The system fortreating water can comprise at least one free radical scavenging systemfluidly connected to at least one source of water that can containbyproducts from one or more upstream processes. In certain aspects ofthe invention, the at least one source of water can be pure, or evenultrapure, and water having a resistivity of at least 1 megaohm-cm, 5megaohm-cm, 10 megaohm-cm, or 15 megaohm-cm. In certain aspects of theinvention, the at least one source of water, for example, feed water tothe primary actinic radiation reactor or free radical scavenging system,can be ultrapure water. The system for treating water can also comprise,or be fluidly coupled to, at least one particulate removal system thatis fluidly connected downstream of the at least one free radicalscavenging system and at least one ultrapure water delivery system thatis fluidly connected downstream of at least one particulate removalsystem. Further the system for treating water typically also comprisesat least one water return system that fluidly connects the at least oneultrapure water delivery system to at least one of the free radicalscavenging systems. The free radical scavenging system, in some cases,can consist essentially of, or preferably, comprise at least one sourceof at least one precursor compound. Typically, the at least one sourceof at least one precursor compound is disposed or otherwise constructedand arranged to introduce at least one free radical precursor compoundinto at least a portion of the water from the at least one source ofwater. The free radical scavenging system can further consistessentially of or comprise at least one source of actinic radiation withor without at least one further alternative apparatus that can alsoinitiate or convert at least one precursor compound into at least onefree radical scavenging species in the water. In still other cases, theparticulate removal system can comprise at least one ultrafiltrationapparatus. Typically, at least one ultrafiltration apparatus is fluidlyconnected downstream of the at least one source of actinic radiation orat least one free radical initiating apparatus and, preferably, upstreamof at least one ultrapure water delivery system.

In accordance with at least one further aspect of the invention, someembodiments thereof can involve a system for providing ultrapure waterto a semiconductor fabrication unit. The system can comprise one or moresources of water fluidly connected to at least one actinic radiationreactor. The at least one reactor is preferably configured to irradiatewater from the source of water. The system can further comprise one ormore sources of a precursor compound. The one or more sources ofprecursor compound can be disposed to introduce one or more free radicalprecursor compounds into the water from the one or more water sources.The system can also comprise at least one particulate filter fluidlyconnected downstream of at least one of the one or more actinicradiation reactors and, preferably, upstream of an ultrapure waterdistribution system. The ultrapure water distribution system is, in someadvantageous embodiments of the invention, fluidly connected to thesemiconductor fabrication unit. The water source typically provideswater having a total organic carbon (TOC) value of less than about 25ppb. In some embodiments, the water source typically has a resistivityof at least about 1 megaohm-cm, about 5 megaohm-cm, about 10 megaohm-cm,or about 15 megaohm-cm. The system for providing ultrapure water canfurther comprise a recycle line that fluidly connects the ultrapurewater distribution system, typically an outlet port thereof, with the atleast one of the source of water, the actinic radiation reactor, and theparticulate filter.

In accordance with some aspects, some embodiments of the invention caninvolve a method of providing ultrapure water to a semiconductorfabrication unit. The method can comprise one or more acts of providinginlet water having a TOC value of less than about 25 ppb, introducing atleast one free radical precursor compound into the water, and convertingthe at least one free radical precursor compound into at least one freeradical scavenging species. The method can further comprise one or moreacts of removing at least a portion of any particulates from the waterto produce the ultrapure water, and delivering at least a portion of theultrapure water to the semiconductor fabrication unit.

In accordance with other aspects, some embodiments of the invention caninvolve a computer-readable medium having computer-readable signalsstored thereon that define instructions that as a result of beingexecuted by at least one processor, instruct the at least one processorto perform a method of regulating addition of at least one free radicalprecursor compound into an inlet water. The inlet water, in some cases,can be pure or ultrapure water, but preferably has a TOC value of lessthan about 25 ppb. The method executable by the at least one processorcan comprise one or more acts of generating one or more drive signalsbased at least partially on the TOC value of the inlet water; andtransmitting the one or more drive signals to at least one source of theat least one precursor compound, the at least one source disposed tointroduce the at least one precursor compound into the inlet water.

In accordance with other aspects of the invention, some embodiments ofthe invention can include a system for treating water. The system cancomprise a primary actinic radiation reactor. The system can furthercomprise a source of a persulfate precursor compound disposed tointroduce at least one persulfate precursor compound into the primaryactinic radiation reactor. The system can further comprise one or moresensors such as a total organic carbon (TOC) concentration sensorlocated upstream of the primary actinic radiation reactor. The systemcan further comprise a persulfate concentration sensor locateddownstream of the primary actinic radiation reactor. The system canfurther comprise a source of a reducing agent. The reducing agent can bedisposed to introduce at least one reducing agent downstream of theprimary actinic radiation reactor. A reducing agent concentration sensorcan also be provided. The reducing agent concentration sensor can belocated downstream of a point of addition of the at least one reducingagent. A controller can also be provided. The controller can beoperatively coupled to receive at least one input signal from at leastone of the TOC concentration sensor, the persulfate concentrationsensor, and the reducing agent concentration sensor. The controller canregulate at least one of a rate at which the persulfate precursorcompound is introduced into the primary actinic radiation reactor, anintensity of the actinic radiation in the primary actinic radiationreactor, and a rate at which the reducing agent is introduced to thesystem.

In accordance with yet other aspects of the invention, a method oftreating water is provided. The method can comprise providing water tobe treated. The method can also comprise measuring a TOC value of thewater to be treated, and introducing persulfate anions to the water tobe treated based at least in part on at least one input signal of themeasured TOC value of the water to be treated. The method can alsocomprise introducing the water containing persulfate anions to a primaryreactor, and exposing the persulfate anions in the water to ultravioletlight in the reactor to produce an irradiated water stream. The methodcan further comprise adjusting an intensity of the ultraviolet lightbased at least in part on at least one of an input signal selected fromthe group consisting of a TOC value of the water to be treated, apersulfate value of the water downstream of the reactor, and a rate ofaddition of persulfate anions. A reducing agent can be introduced to theirradiated water.

In accordance with yet other aspects of the invention, a method formeasuring a concentration of a compound in a liquid stream is provided.The method can comprise measuring a first conductivity in the liquidstream, and irradiating at least a portion of the liquid stream. Themethod can further comprise measuring a second conductivity of theliquid stream after irradiating, and calculating the concentration ofthe compound based at least in part on the first conductivitymeasurement and the second conductivity measurement. In certainembodiments of the invention, the compound can be persulfate or sulfurdioxide.

In accordance with yet other aspects of the invention, a method forcontrolling introduction of sulfur dioxide to a liquid stream isprovided. The system can comprise a persulfate concentration sensor influid communication with the liquid stream. The system can furthercomprise a source of sulfur dioxide. The sulfur dioxide can be disposedto introduce sulfur dioxide to the liquid stream downstream of thepersulfate concentration sensor. The system can further comprise asulfur dioxide concentration sensor in fluid communication with theliquid stream and located downstream of the source of sulfur dioxide.The system can further comprise a controller. The controller can beconfigured to generate a control signal that regulates at least one of arate of addition of and an amount of the sulfur dioxide introduced intothe liquid stream based on at least one input signal from any one of thepersulfate concentration sensor and the sulfur dioxide stream.

In accordance with yet other aspects of the invention, an actinicradiation reactor is provided. The actinic radiation reactor cancomprise a vessel, and a first array of tubes in the vessel. The firstarray of tubes can comprise a first set of parallel tubes, and a secondset of parallel tubes. Each tube can comprise at least one ultravioletlamp and each of the parallel tubes of the first set is positioned tohave its longitudinal axis orthogonal relative to the longitudinal axisof the tubes of the second set.

In one or more embodiments, any of which may be relevant to one or moreaspects of the invention, the systems and techniques disclosed hereinmay utilize one or more subsystems that adjusts or regulates or at leastfacilitates adjusting or regulating at least one operating parameter,state, or condition of at least one unit operation or component of thesystem or one or more characteristics or physical properties of aprocess stream. To facilitate such adjustment and regulatory features,one or more embodiments of the invention may utilize controllers andindicative apparatus that provide a status, state, or condition of oneor more components or processes. For example, at least one sensor may beutilized to provide a representation of an intensive property or anextensive property of, for example, water from the source, waterentering or leaving the free radical scavenging system, water enteringor leaving the particulate removal system, or water entering or leavingan actinic radiation reactor or one or more other downstream processes.Thus, in accordance with a particularly advantageous embodiment, thesystems and techniques of the invention may involve one or more sensorsor other indicative apparatus, such as composition analyzers, orconductivity cells, that provide, for example, a representation of astate, condition, characteristic, or quality of the water entering orleaving any of the unit operations of the system.

FIG. 1 schematically embodies a system 100 in accordance with one ormore aspects of the invention. System 100 can be representative of awater treatment or purification system that provides water includingwater that can be considered to be ultrapure water. In some particularlyadvantageous embodiments of the invention, system 100 can be directed toor be representative of a purification system providing ultrapure watersuitable for use in semiconductor fabrication facilities or at leastmaintaining an ultrapure water quality. Still further aspects of theinvention involve a system 100 that can be considered as utilizingultrapure water to provide treated ultrapure water to one or moresemiconductor fabrication units (not shown). Thus, in accordance withsome aspects of the invention, system 100 can be a water treatmentsystem that reduces a concentration, content, or level of one or moreimpurities or contaminants that may be present in make-up or inlet waterfrom one or more water sources 110 and provide the treated water to asystem that utilizes ultrapure water.

As exemplarily illustrated, system 100 can comprise one or more first orprimary treatment trains or systems 101 coupled to one or more second orsecondary treatment trains or systems 102. System 100 may furthercomprise at least one water distribution system 103 fluidly connected toat least one secondary treatment system and, in some even moreadvantageous configurations, to at least one primary treatment system.Further advantageous embodiments can involve configurations that involveat least one flow directional control device in at least one of theprimary treatment system, the secondary treatment system, and the waterdistribution system. Non-limiting examples of directional flow controldevices include check valves and weirs.

Preferably, source 110 provides water consisting of, consistingessentially of, or comprising a low level of impurities. Water fromsource 110 may have a resistivity of at least about 1 megaohm-cm, about5 megaohm-cm, or about 10 megaohm-cm. More preferably, water from source110 consists of, consists essentially of, or comprises ultrapure waterhaving at least one characteristic selected from the group consisting ofa total organic carbon level or value of less than about 25 ppb or evenless than about 20 ppb, as urea, and a resistivity of at least about 15megaohm-cm or even at least about 18 megaohm-cm. First or primarytreatment system 101 can further comprise at least one source 122 of aprecursor treating compound fluidly connected to reactor 120.

Water introduced into system 100 from source 110 typically, or evenpreferably, can be characterized by having a low level of impurities.For example, some embodiments of the invention utilize pure or ultrapurewater or mixtures thereof that have previously been treated or purifiedby one or more treatment trains (not shown) such as those that utilizereverse osmosis (for example, two-pass reverse osmosis),electrodialysis, electrodeionization, distillation, ion exchange, orcombinations of such operations. As noted, advantageous embodiments ofthe invention involve ultrapure inlet water from source 110 thattypically has low conductivity or high resistivity of at least about 15megaohm-cm, preferably at least about 18 megaohm-cm, and/or has a lowlevel of contaminants as, for example, a low total organic carbon levelof less than about 50 ppb, and preferably, less than about 25 ppb,typically as urea or other carbon compound or surrogate. In certainembodiments, the inlet water may be as low as 1 ppb. In otherembodiments, the inlet water may be as low as 0.5 ppb. In yet otherembodiments, the resistivity of the inlet water may be about 1megaohm-cm.

In some particular embodiments of the invention, first treatment system101 can be characterized or comprise at least one free radicalscavenging system. The free radical scavenging system 101 can compriseat least one free radical scavenger reactor 120, such as an irradiationreactor, fluidly connected to at least one source 110 of water. Reactor120 can be a plug flow reactor or a continuously stirred tank reactor,or combinations thereof. In certain embodiments, a plug flow reactor canbe used to prevent the likelihood of blinded or regions of lowerirradiation intensity, such as short circuiting, of illumination by thelamps within the reactor. A plug flow reactor can be defined as areactor that operates under conditions that facilitate laminar flowpaths of fluid through the reactor, having parallel, non-turbulent flowpaths. Reactor 120 is typically sized to provide a residence timesufficient to allow free radical species in the water flowing in thereactor to scavenge, degrade, or otherwise convert at least one of theimpurities, typically the organic carbon-based impurities into an inertcompound, one or more compounds that may be removed from the water, orat least to one that can be more readily removed relative to the atleast one impurity.

The reactor can additionally be sized based on the expected flow rate ofthe system to provide a sufficient or a desired residence time in thereactor. In certain embodiments, the flow rate of water through thesystem can be based on the demand for treated water downstream of thesystem, or the flow rate of water being utilized upstream of the system,or both. In certain examples, the flow rate of water through the system,or through each reactor, can be between about 1 gallon per minute (gpm)and 2000 gpm. In particular examples, the flow rate can be from about400 gpm to about 1300 gpm. In other particular examples, the flow ratecan be from about 400 gpm to about 1900 gpm. The reactor and other unitoperations and equipment of the system, such as pumps and flow valves,can be selected and sized to allow for fluctuations or changes in flowrates from about 400 gpm to about 1900 gpm.

In the free radical scavenging system, organic compounds in the watercan be oxidized by one or more free radical species into carbon dioxide,which can be removed in one or more downstream unit operations. Reactor120 can comprise at least one free radical activation device thatconverts one or more precursor compounds into one or more free radicalscavenging species. For example, reactor 120 can comprise one or morelamps, in one or more reaction chambers, to irradiate or otherwiseprovide actinic radiation to the water and divide the precursor compoundinto the one or more free radical species.

The reactor can be divided into two chambers by one or more bafflesbetween the chambers. The baffle can be used to provide mixing orturbulence to the reactor or prevent mixing or promote laminar, parallelflow paths through the interior of the reactor, such as in the chambers.In certain embodiments, a reactor inlet is in fluid communication with afirst chamber and a reactor outlet is in fluid communication with asecond chamber.

In some embodiments, at least three reactor chambers, each having atleast one ultraviolet (UV) lamp disposed to irradiate the water in therespective chambers with light of about 185 nm, 220 nm, and/or 254 nm,or ranging from about 185 nm to about 254 nm, at various power levels,are serially arranged in reactor 120. Sets of serially arranged reactorscan be arranged in parallel. For example, a first set of reactors inseries may be placed in parallel with a second set of reactors inseries, with each set having three reactors, for a total of sixreactors. Any one or more of the reactors in each set may be in serviceat any time. In certain embodiments, all reactors may be in service,while in other embodiments, only one set of reactors is in service.

Commercially available sources of actinic radiation systems ascomponents of free radical scavenging systems include those from, forexample, Quantrol, Naperville, Ill., as the AQUAFINE® UV system, andfrom Aquionics Incorporated, Erlanger, Ky.

As noted, the invention is not limited to a single precursor compoundand may utilize a plurality of precursor compounds. In certainembodiments, the precursor compound may be used to degrade anundesirable species. In other embodiments, the precursor compound may beused convert an undesirable component to a removable constituent, suchas an ionized species, or a weakly charged species. A plurality ofprecursor compounds may be utilized to generate a plurality of freeradical species. This complementary arrangement may be advantageous inconditions where a first free radical scavenging species selectivelydegrades a first type of undesirable compound and a second free radicalspecies selectively degrades other undesirable compounds. Alternatively,a first precursor compound may be utilized that can be readily convertedto a first converted species or a first free radical species. The firstfree radical species can then convert a second precursor compound into asecond converted species or a second free radical species. Thiscascading set of reactions may also be advantageous in conditions wherethe first free radical species selectively degrades or converts a firsttype of undesirable compound and the second free radical speciesselectively degrades or converts other undesirable compounds or in caseswhere conversion or activation of the second precursor compound into thesecond free radical species undesirably requires high energy levels. Aplurality of compounds may be used to provide a plurality of scavengingspecies.

The one or more precursor compounds can be any compound that can beconverted to or facilitates conversion of a free radical scavengingspecies. Non-limiting examples include persulfate salts such as alkaliand alkali metal persulfates and ammonium persulfate or ammoniumpersulfate, hydrogen peroxide, peroxide salts such as alkali and alkalimetal peroxides, perborate salts such as alkali and alkali metalperborates, peroxydisulfate salts such as alkali and alkali metalperoxydisulfate and ammonium peroxydisulfate, acids such asperoxydisulfuric acid, peroxymonosulfuric acid or Caro's acid, andozone, as well as combinations thereof such as piranha solution. Theamount of the one or more precursor compounds can vary depending on thetype of contaminant. The precursor compound can consist of or consistessentially of ammonium persulfate which may be advantageous insemiconductor fabrication operations because it would likely providebyproducts that are not considered contaminants of such operations orbecause they can be readily removed by, for example, ion exchangesystems, in contrast to precursor compounds comprising sodium persulfatewhich can produce sodium species that are not readily removable and/orcan undesirably contaminate a semiconductor device.

In some cases, system 100 can comprise at least one degasifier 160 and,optionally, at least one particulate filter downstream of reactor 120.In some cases, system 100 can further comprise at least one apparatusthat removes at least a portion of any ionic or charged species from thewater. For example, system 100 in one or both of scavenging system 101or particulate removal system 102 can comprise a bed of ion exchangemedia or an electrically-driven ion purification apparatus, such as anelectrodialysis apparatus or an electrodeionization apparatus. Inparticularly advantageous configurations of the invention, system 100can comprise a first, primary or leading ion exchange column 140Lcomprising an ion exchange resin bed and a second, lagging or polishingion exchange column 140P, also comprising ion exchange resin bed, eachserially disposed, relative to each other, along a flow path of thewater through system 100. The ion exchange columns may comprise a mixedbed of anion exchange media and cation exchange media. Otherconfigurations, however, may be utilized. For example, lead ion exchangecolumn 140L may comprise serially arranged layers or columns; the firstlayer or column can predominantly comprise anion exchange media and thesecond column can predominantly comprise cation exchange media.Likewise, although polish column 140P can comprise a mixed bed of anionexchange media and cation exchange media, polish column 140P maycomprise serially arranged layers of columns of a type of exchangemedia; the first column can predominantly comprise anion exchange mediaand the second column can predominantly comprise cation exchange media.Any of the first and second layers or columns may be disposed within asingle vessel comprising 140L or 140P and be practiced as layered bedsof media contained within the columns. The ion exchange media in ionexchange columns 140L and 140P may be any suitable resin including thosethat remove sulfate species, carbon dioxide, and ammonia or ammonium andany other undesirable species or contaminant in the water from source110 or as a byproduct of the free radical scavenging process. The ionexchange columns can be mixed bed ion exchange columns that containanionic and cationic resin.

Commercially available media or ion exchange resins that may be utilizedinclude, but are not limited to, NR30 MEG PPQ, USF™ MEG PPQ, and USF™NANO resins from Siemens Water Technologies Corp., Warrendale, Pa., andDOWEX® resin from The Dow Chemical Company, Midland, Mich.

In some further embodiments of the invention, second treatment system102 can comprise or be characterized as a particulate removal system.For example, system 100 can further comprise at least one particulatefilter 150. Filter 150 typically comprises a filtering membrane thatremoves or traps particles of at least a target size. For example,filter 150 can be constructed with filtering media or one or moremembranes that trap all or at least a majority of particles with anaverage diameter of at least about 10 microns, in some cases, at leastabout 1 micron, in still other cases, at least about 0.05 micron, andeven other cases, at least about 0.02 micron, depending on the servicerequirements of the point of use connected to the distribution system103. Filter 150 can comprise a cartridge filter with a membrane thatretains particles that are greater than about 0.01 micron.

A particulate filter (not shown) may optionally be utilized to removeparticulates introduced with the one or more precursor compounds fromsource 122. This filter, like filter 150 may also remove particulatesgreater than 0.02 micron.

In some cases, particulate removal system 102 can comprise one or moreultrafiltration apparatus 172 and 174, each comprising a membrane thatprevents particles having an undesirable size characteristic fromflowing into the water distribution system with product water.Preferably at least two ultrafiltration apparatus are serially arrangedto facilitate removing particulates of, for example, greater than about0.1 micron, and in some cases, greater than 0.05 micron, and still othercases, greater than 0.02 micron. For example, the ultrafiltrationapparatus 172 and 174 may comprise membranes that reduce or otherwiseprovide a target or desired concentration of particulates larger than0.05 micron to a level of less than about 100 counts per liter ofproduct water to the point of use. The construction and arrangement ofthe ultrafiltration apparatus 172 and 174 may depend on the targetparticulate concentration and the size of the particulates in theultrapure water product. In some embodiments of the invention, filter172 removes at least a majority of the particulates of target size andfilter 174 serves as a polish to ensure that the concentration ofparticulates to water distribution system 103 is at a level that is lessthan or equal to the target or desired particulate concentration. Insuch configurations, a retentate water stream from filter 172 typicallycontains a majority of the trapped particulates and can be discharged ordiscarded or used in other processes. Preferably, however, at least aportion of the retentate water stream is introduced into a particulatefilter 180 comprising a membrane or media that traps at least a portionof the particulates; the permeate stream therefrom, from which asubstantial portion of particulates is removed, can be directed to andmixed with an upstream unit operation of the system 100 such as, but notlimited to, a returning or circulating unused ultrapure product waterfrom distribution system 103, inlet water from source 110 introducedinto the free radical scavenging system 101, at least partially treatedwater from reactor 120, filter 150, degasifier 160, lead ion exchangecolumn 140L or polish ion exchange column 140P, or combinations thereof.Like filter 150, filter 180 can also be constructed to remove or reducea level of particulate material of a certain size to a particular ortarget level.

Degasifier 160 can comprise a membrane contactor or any unit operationthat reduces a concentration of any dissolved gases in the water orother gaseous byproduct of the precursor compound. Preferably, thedegasifier reduces any of the dissolved oxygen content, the dissolvednitrogen content, and the dissolved carbon dioxide content in the water.Typically, degasifier 160 utilizes a contacting membrane and a vacuumsource 162 that facilitates removal of the dissolved gases from thewater. Non-limiting examples of degasifiers that may be utilized hereinincludes those commercially available as LIQUI-CEL® membrane contactorsfrom Membrana, Charlotte, N.C.

Other ancillary unit operations may be utilized to adjust at least oneintensive or extensive property of the water provided to a point of use,which can be the semiconductor fabrication unit. For example, a heatexchanger, such as a chiller 130, may be disposed upstream of ultrapurewater distribution system 103 to reduce the temperature of at least aportion of the ultrapure water deliverable to at least one semiconductorfabrication unit. As illustrated, chiller 130 is disposed downstream ofreactor 120 but upstream of degasifier 160. The invention, however, isnot limited to the exemplary presented arrangement and one or more heatexchangers may be, for example, in thermal communication with theultrapure water product downstream of particulate removal system 102 butupstream of water distribution system 103. Indeed, a plurality of heatexchangers may be utilized. For example, a first heat exchanger, such asa heater, may heat the water having at least one free radical precursorcompound to assist in initiating or converting the precursor compoundinto one or more free radical scavenging species and a second heatexchanger, such as a chiller, may cool the treated ultrapure water priorto delivery through the water distribution system.

Still other ancillary systems include, for example, one or more pumps166 that provide motive force for circulating the water through system100. Pump 166 may be a positive displacement pump or a centrifugal pump.Preferably, pump 166 comprises components that do not undesirablycontribute to the contamination characteristics of the product water.

Water distribution system 103 can comprise an inlet port and at leastone outlet port fluidly connected to and providing ultrapure productwater to one or more points of use (not shown), such as one or moresemiconductor fabrication units.

In some cases, for example, the water distribution system comprises amanifold 190 having an inlet port fluidly connected to free radicalscavenging system 101, particulate removal system 102, or both, and atleast one product outlet fluidly connected to at least one point of use,and at least one return outlet port fluidly connected to one or morecirculating systems 178 and 179 to recycle unused product water to oneor both of the free radical scavenging system and the particulateremoval system or into any point in system 100.

FIG. 2 schematically embodies a system 200 in accordance with one ormore aspects of the invention. System 200 can be representative of awater treatment or purification system that provides water includingwater that can be considered to be ultrapure water. In some particularlyadvantageous embodiments of the invention, system 200 can be directed orbe representative of a purification system providing ultrapure watersuitable for semiconductor fabrication facilities or at leastmaintaining an ultrapure water quality. Still further aspects of theinvention involve a system 200 that can be considered as utilizingultrapure water to provide treated ultrapure water to one or moresemiconductor fabrication units (not shown). In yet further aspects ofthe invention, system 200 can be directed to or be representative of apurification system providing ultrapure water suitable for processing bysystem 100 of FIG. 1, or at least a part of a system that can provideultrapure water. Thus, in accordance with some aspects of the invention,system 200 can be a water treatment system that reduces a concentration,content, or level of one or more impurities or contaminants that may bepresent in make-up or inlet water from one or more water sources 210 andprovide the treated water to a system that utilizes ultrapure water.

As with system 100, treatment system 200 can comprise subsystems orcomponents that converts or renders at least a portion of one or moretarget species into a species that can be removed in any one or moreseparation unit operations such as, but not limited to, degasificationsystems, particulate removal systems, and ion trapping, capturing orexchanging systems.

As exemplarily illustrated, system 200 can comprise a series of unitoperations 212, 214, and 216. Water to be treated from source of water210 can be optionally introduced to a reverse osmosis unit to removeparticulates from the water stream. Precursor compounds from source 216of precursor compounds can be introduced into filtrate 214 from reverseosmosis unit 212. The filtrate stream with the precursor compoundsdisposed therein can be introduced into free radical scavenging system218. Free radical scavenging system 218 can comprise at least one freeradical scavenger reactor or actinic radiation reactor fluidly connectedto at least one source 210 of water.

Free radical scavenging system 218 can comprise one or more reactors orvessels, each of which can be arranged serially or in parallel. Incertain embodiments, sets of serially arranged reactors can be arrangedin parallel. For example, a first set or train of reactors in series maybe placed in parallel with another set or train of reactors, also inseries, with each set having three reactors, for a total of six reactorsin free radical scavenging system 218. Any one or more of the reactorsin each set may be in service at any time. In certain embodiments, allreactors may be in service, while in other embodiments, only one set ofreactors is in service. Free radical scavenging system 218 can also beconsidered a primary actinic radiation reactor.

The reactor can be a plug flow reactor or a continuously stirred tankreactor, or combinations thereof. In certain embodiments, a plug flowreactor can be used so as to prevent or reduce the likelihood of blindedor regions of lower irradiation intensity, such as short circuiting, ofillumination by the lamps within the reactor. The reactor is typicallysized to provide a residence time sufficient to generate and/or allowfree radical species in the water flowing in the reactor to scavenge,degrade, or otherwise convert at least a portion of the at least one ofthe impurities, typically the organic carbon-based impurities into aninert or ionized compound, one or more compounds that may be removedfrom the water, or at least to one that can be more readily removedrelative to the at least one impurity. The reactor can additionally besized based on the expected flow rate of the system to provide asufficient residence time in the reactor. The reactor can also be sizedbased on the flow rate of water through the system. In certainembodiments, the flow rate of water through the system can be based onthe demand for treated water downstream of the system, or the flow ratewater being utilized upstream of the system. In certain examples, theflow rate can be between about 1 gallon per minute (gpm) and 2000 gpm.In particular examples, the flow rate can be between about 500 gpm andabout 1300 gpm. In other particular examples, the flow rate can be fromabout 1300 gpm to about 1900 gpm.

In the free radical scavenging system, organic compounds in the watercan be oxidized by one or more free radical species into carbon dioxide,which can be removed in one or more downstream unit operations. Thereactor can further comprise at least one free radical activation devicethat converts one or more precursor compounds into one or more freeradical scavenging species. For example, the reactor can comprise one ormore lamps, in one or more reaction chambers, to irradiate or otherwiseprovide actinic radiation to the water that activates, converts ordivides the one or more precursor compounds into the one or more freeradical species.

The reactor can, thus, be sized based on the number of ultraviolet lampsrequired to scavenge, degrade, or otherwise convert at least one of theimpurities, typically the organic carbon-based impurities into an inert,ionized, or otherwise removable compound, one or more compounds that maybe removed from the water, or at least to one that can be more readilyremoved relative to the at least one impurity. The number of lampsrequired can be based at least in part on lamp performancecharacteristics including the lamp intensity and spectrum wavelengths ofthe ultraviolet light emitted by the lamps. The number of lamps requiredcan be based at least in part on at least one of the expected TOCconcentration or amount in the inlet water stream and the amount ofpersulfate added to the feed stream or reactor.

Irradiated water stream 220 can exit free radical scavenging system 218and can be optionally introduced into a secondary irradiation systemwhich can also include one or more actinic radiation reactors 221.Secondary actinic radiation reactor 221 can comprise one or morevessels, each containing one or more ultraviolet lamps. As with system218, each of the vessels can be arranged serially or in parallel. Incertain embodiments, sets of serially arranged secondary reactors can bearranged in parallel. For example, two or more sets of serially arrangedsecondary reactors may be placed in parallel, with each set of seriallyarranged secondary reactors having two or more reactors. Any one or moreof the secondary reactors in each set may be in service at any time. Incertain embodiments, all secondary reactors may be in service, while inother embodiments, only one set of secondary reactors may be in service.In certain embodiments, the ultraviolet lamps may emit ultraviolet lightat a wavelength of in a range of about 185 nm to about 254 nm.

System 200 can have a source of reducing agent 224 which can introduceone or more neutralizing or reducing agents such as sulfur dioxide, tothe further irradiated water stream 222 at, for example, point ofaddition 230. The neutralizing or reducing agent can be any compound orspecies that can reduce or neutralize any of the residual precursorcompounds or derivatives thereof in irradiated water stream 222 to adesired level.

Stream 226 can be introduced to one or more downstream processes 228, orcan be used as ultrapure water in a desired application, such as in asemiconductor fabrication process.

In some advantageous embodiments, system 200 can further comprise one ormore unit operations that further remove any non-dissolved material,such as particulate filters. A particulate filter such as anultrafiltration apparatus, may be located downstream from primaryactinic radiation reactor 218.

Further advantageous embodiments can involve configurations that involveat least one flow directional control device in the system. Non-limitingexamples of directional flow control devices include check valves andweirs.

Any of sources 110 and 210 can provide water consisting of, consistingessentially of, or comprising a low level of impurities. Water from anyof sources 110 and 210 may have a resistivity of at least about 1megaohm-cm, about 5 megaohm-cm, or about 10 megaohm-cm. More preferably,water from source 110 or 210 consists of, consists essentially of, orcomprises ultrapure water having at least one characteristic selectedfrom the group consisting of a total organic carbon level or value ofless than about 25 ppb or even less than about 20 ppb, as urea, and aresistivity of at least about 15 megaohm-cm or even at least about 18megaohm-cm. Free radical scavenging system 101 can further comprise atleast one source 122 of a precursor compound fluidly connected toreactor 120.

Water introduced into system 100 and/or system 200 from source 110 andsource 210 typically, or even preferably, can be characterized as havinga low level of impurities. For example, some embodiments of theinvention utilize pure or ultrapure water or mixtures thereof that havepreviously been treated or purified by one or more treatment trains (notshown) such as those that utilize reverse osmosis, electrodialysis,electrodeionization, distillation, ion exchange, or combinations of suchoperations. As noted, advantageous embodiments of the invention involveultrapure inlet water from, for example, source 110 and/or source 210that typically has low conductivity or high resistivity, of at leastabout 15 megaohm-cm, preferably at least about 18 megaohm-cm, and/or hasa low level of contaminants as, for example, a low total organic carbonlevel of less than about 50 ppb, and preferably, less than about 25 ppb,typically as urea or other carbon compound, or surrogate thereof.

One or more lamps can be utilized in the reactors to illuminate orirradiate the fluid contained therein. Particular embodiments of theinvention can involve reactors having a plurality of lamps, eachadvantageously disposed or positioned therein to irradiate the fluidwith one or more illumination intensity levels for one or a plurality ofillumination periods. Further aspects of the invention can involveutilizing the one or more lamps within any of the reactors inconfigurations that accommodate or facilitate a plurality ofsimultaneous illumination intensities.

The ultraviolet lamps can be advantageously positioned or distributedwithin the one or more reactors of the free radical scavenging system toirradiate or otherwise provide actinic radiation to the water asdesired. In certain embodiments, it is desired to distribute the lampswithin the one or more reactors to evenly distribute actinic radiationthroughout the reactor. In any of systems 218 and reactors 221, theultraviolet lamps of the free radical scavenging system can be adjustedto provide illumination at various intensities or various power levels.For example, ultraviolet lamps can be used that can be adjusted tooperate at a plurality of illumination modes, such as dim, rated, andboost mode, for example, a low, medium, or high mode.

The one or more lamps can be positioned within the one or more actinicradiation reactors by being placed within one or more sleeves or tubeswithin the reactor. The tubes can hold the lamps in place and protectthe lamps from the water within the reactor. The tubes can be made ofany material that is not substantially degraded by the actinic radiationand the water or components of the water within the reactor, whileallowing the radiation to pass through the material. The tubes can havea cross-sectional area that is circular. In certain embodiments, thetubes can be cylindrical, and the material of construction thereof canbe quartz. Each of the tubes can be the same or different shape or sizeas one or more other tubes. The tubes can be arranged within the reactorin various configurations, for example, the sleeves may extend across aportion of or the entire length or width of the reactor. The tubes canalso extend across an inner volume of the reactor.

Commercially available ultraviolet lamps and/or quartz sleeves may beobtained from Hanovia Specialty Lighting, Fairfield, N.J., EngineeredTreatment Systems, LLC (ETS), Beaver Dam, Wis., and Heraeus NoblelightGmbH of Hanau, Germany. The quartz material selected can be based atleast in part on the particular wavelength or wavelengths that will beused in the process. The quartz material may be selected to minimize theenergy requirements of the ultraviolet lamps at one or more wavelengths.The composition of the quartz can be selected to provide a desired orsuitable transmittance of ultraviolet light to the water in the reactorand/or to maintain a desired or adequate level of transmissivity ofultraviolet light to the water. In certain embodiments, thetransmissivity can be at least about 50% for a predetermined period oftime. For example, the transmissivity can be about 80% or greater for apredetermined period of time. In certain embodiments, the transmissivitycan be in a range of about 80% to 90% for about 6 months to about oneyear. In certain embodiments, the transmissivity can be in a range ofabout 80% to 90% for up to about two years.

The tubes can be sealed at each end so as to not allow the contents ofthe reactor from entering the sleeves or tubes. The tubes can be securedwithin the reactor so that they remain in place throughout the use ofthe reactor. In certain embodiments, the tubes are secured to the wallof the reactor. The tubes can be secured to the wall through use of asuitable mechanical technique, or other conventional techniques forsecuring objects to one another. The materials used in the securing ofthe tubes is preferably inert and will not interfere with the operationof the reactor or negatively impact the purity of the water, or releasecontaminants to the water.

The lamps can be arranged within the reactor such that they are parallelto each other. The lamps can also be arranged within the reactor atvarious angles to one another. For example, in certain embodiments, thelamps can be arranged to illuminate paths or coverage regions that forman angle of approximately 90 degrees such that they are approximatelyorthogonal or perpendicular to one another. The lamps can be arranged inthis fashion, such that they form an approximately 90 degree angle on avertical axis or a horizontal axis, or any axis therebetween.

In certain embodiments, the reactor can comprise an array of tubes inthe reactor or vessel comprising a first set of parallel tubes and asecond set of parallel tubes. Each tube may comprise at least oneultraviolet lamp and each of the parallel tubes of the first set can bearranged to be at a desired angle relative to the second set of paralleltubes. The angle may be approximately 90 degrees in certain embodiments.The tubes of any one or both of the first array and the second array mayextend across an inner volume of the reactor. The tubes of the first setand the second set can be arranged at approximately the same elevationwithin the reactor.

Further configurations can involve tubes and/or lamps that are disposedto provide a uniform level of intensity at respective occupied orcoverage regions in the reactor. Further configurations can involveequispacially arranged tubes with one or more lamps therein.

The reactor may contain one or more arrays of tubes arranged within thereactor or vessel. A second array of tubes can comprise a third set ofparallel tubes, and a fourth set of parallel tubes orthogonal to thethird set of parallel tubes, each tube comprising at least oneultraviolet lamp. The fourth set of parallel tubes can also beorthogonal to at least one of the second set of parallel tubes and thefirst set of parallel tubes.

In certain embodiments, each array within the reactor or vessel can bepositioned a predetermined distance or elevation from another arraywithin the reactor. The predetermined distance between a set of twoarrays can be the same or different.

FIG. 3 exemplarily shows a cross-sectional view of a reactor vessel 300that can be used in system 100 or system 200 or both. Reactor vessel 300typically comprises inlet 310, outlet 320, and baffle 315 which dividesreactor vessel 300 into upper chamber 325 and lower chamber 330. Reactorvessel 300 can also comprise manifold 305 which can be configured todistribute water introduced through inlet 310 throughout the vessel. Incertain embodiments, manifold 305 can be configured to evenly distributewater throughout the vessel. For example, manifold 305 can be configuredto evenly distribute water throughout the vessel such that the reactoroperates as a plug flow reactor.

In some embodiments, the reactor vessel may comprise more than onebaffle 315 to divide the reactor vessel into more than two chambers.Baffle 315 can be used to provide mixing or turbulence to the reactor.In certain embodiments, as shown in FIG. 3, reactor inlet 310 is influid communication with lower chamber 330 and reactor outlet 320 is influid communication with upper chamber 325.

In some embodiments, at least three reactor chambers, each having atleast one ultraviolet (UV) lamp disposed to irradiate the water in therespective chambers with light of about or ranging from about 185 nm toabout 254 nm, 220 nm, and/or 254 nm at a desired or at various powerlevels, are serially arranged in reactor 120.

The reactor vessel can also comprise a plurality of ultraviolet lampspositioned within tubes, for example tubes 335 a-c and 340 a-c. In oneembodiment of the invention, as shown in FIG. 3, reactor vessel 300comprises a first set of parallel tubes, tubes 335 a-c and a second setof parallel tubes (not shown). Each set of parallel tubes of the firstset is approximately orthogonal to the second set to form first array345. Tubes 335 a-c and the second set of parallel tubes are atapproximately the same elevation in reactor vessel 300, relative to oneanother.

Further, the reactor vessel can comprise a third set of parallel tubesand a fourth set of parallel tubes. Each set of parallel tubes of thefirst set is approximately orthogonal to the second set to form, forexample, second array 350. As exemplarily illustrated, tubes 340 a-c andthe second set of parallel tubes are at approximately the same elevationin reactor vessel 300, relative to one another. As shown in FIG. 3,first array 345 can be positioned at a predetermined distance fromsecond array 350. Vessel 300 can additionally comprise third array 355and fourth array 360, each optionally having similar configurations asfirst array 340 and second array 345.

In another embodiment, a first tube 335 b can be arranged orthogonal toa second tube 340 b to form a first array. Additionally, a set of tubes,tube 365 a and tube 365 b can be arranged orthogonal to another set oftubes, tube 370 a and tube 370 b to form a second array. The position ofthe lamps of the second array are shown in FIG. 4A, including lamps 414,420, 422, and 424. The positions of the lamps in the first array and thesecond array are shown in FIG. 4B, including lamps 426 and 428 of thefirst array and lamps 414, 420, 422, and 424 of the second array.

The lamps can generate a pattern, depending on various properties of thelamp, including the dimensions, intensity, and power delivered to thelamp. The light pattern generated by the lamp is the general volume ofspace to which that the lamp emits light. In certain embodiments thelight pattern or illumination volume is defined as the area or volume ofspace that the lamp can irradiate or otherwise provide actinic radiationto and allow for division or conversion of the precursor compound intothe one or more free radical species.

As shown in FIGS. 4A and 4B, which shows exemplarily cross-sectionalviews of reactor 400 in which a first set of tubes 410 a-c are arrangedparallel to one another, and a second set of tubes 412 a-c are arrangedparallel to one another. As shown, first set of tubes 410 a-c isarranged orthogonal relative to second set of tubes 412 a-c. Lamps, suchas lamps 414, are dispersed within tubes 410 a-c and 412 a-c, and whenilluminated, can generate light pattern 416.

One or more ultraviolet lamps, or a set of lamps, can be characterizedas projecting actinic radiation parallel an illumination vector. Theillumination vector can be defined as a direction in which one or morelamps emits actinic radiation. In an exemplarily embodiment, as shown inFIG. 4A, a first set of lamps, including lamp 420 and 422, is disposedto project actinic radiation parallel to illumination vector 418.

A first set of ultraviolet lamps each of which is disposed to projectactinic radiation parallel a first illumination vector can be energized.A second set of ultraviolet lamps each of which is disposed to projectactinic radiation parallel a second illumination vector can also beenergized. At least one of the direction of the illumination and theintensity of at least one of the first set of ultraviolet lamps andsecond set of ultraviolet lamps can be adjusted. Each set of ultravioletlamps can comprise one or more ultraviolet lamps.

The number of lamps utilized or energized and the configuration of thelamps in use can be selected based on the particular operatingconditions or requirements of the system. For example, the number oflamps utilized for a particular process can be selected and controlledbased on characteristics or measured or calculated parameters of thesystem. For example measured parameters of the inlet water or treatedwater can include any one or more of TOC concentration, temperature, andflow rate. The number of energized lamps can also be selected andcontrolled based on the concentration or amount of persulfate added tothe system. For example, 12 lamps in a particular configuration can beused if the flow rate of the water to be treated is at or below acertain threshold value, for example a nominal or design flow rate, suchas 1300 gpm, while more lamps can be used if the flow rate of the waterto be treated rises above the threshold value. For example, if the flowrate increases from 1300 gpm to a selected higher threshold value,additional lamps can be energized. For example, 24 lamps may be used ifthe flow rate of the water to be treated reaches 1900 gpm. Thus the flowrate of the water can be partially determinative of which lamps and/orthe number of energized lamps in each reactor.

In certain embodiments, the ultraviolet lamps can be operated at one ormore illumination intensity levels. For example, one or more lamps canbe used that can be adjusted to operate at a plurality of illuminationmodes, such as at any of dim, rated, and boost mode, for example, a low,medium, or high mode. The illumination intensity of one or more lampscan be adjusted and controlled based on characteristics or measured orcalculated parameters of the system, such as measured parameters of theinlet water or treated water, including TOC concentration, temperature,and flow rate. The illumination intensity of one or more lamps can alsobe adjusted and controlled based on the concentration or amount ofpersulfate added to the system. For example, the one or more lamps canbe used in a dim mode up to a predetermined threshold value of ameasured parameter of the system, such as a first TOC concentration. Theone or more lamps can be adjusted to rated mode if the measured orcalculated TOC concentration reaches or is above a second TOCconcentration, which may be above the threshold value. The one or morelamps can further be adjusted to a boost mode if the measured orcalculated TOC concentration reaches or is above a second thresholdvalue.

The lamps and the illumination intensity thereof can be controlledtogether or separately, using the same or different measured parametersand values as thresholds for adjustment.

In some embodiments, the reactor can operate in a first mode which isindicative of a first lamp configuration and a first lamp intensity. Thereactor can operate at the first mode for a particular range or up to aselected or desired value of one or more parameters of the system. Forexample, the reactor can operate at the first mode for a particularrange or up to a selected or desired value, such as a first thresholdvalue, of one or more of the TOC concentration, amount and/or rate ofaddition of persulfate, and flowrate of the inlet water or the flowrateof the water going through the reactor. At or above the selected ordesired value of one or more of the parameters, or a first thresholdvalue, the reactor can operate in a second mode which is indicative ofat least one of a second lamp configuration and a second lamp intensity.The reactor can operate in the second mode for a particular range or upto a selected or desired value, such as a second threshold value, of oneor more parameter of the system. At or above the second threshold value,the reactor can operate in a third mode which is indicative of at leastone or a third lamp configuration and a third lamp intensity.

The system can also be designed such that the reactor can be operated toallow adjustment from the third mode to the second mode, or the secondmode to the first mode based on one or more selected or desiredthreshold values. The system can be operated such that one or morethreshold levels are selected or inputed into the system, and the systemcan be operated in one or more operating modes.

In some particular embodiments, for example, the first mode may beindicative of the system operating at less than 30% of the designed flowrate capacity of the system, or less than 30% of the TOC concentrationof the target TOC concentration of the inlet water, or less than 30% ofthe maximum amount or rate of addition of persulfate that can be addedto the reactor. The second mode may be indicative of the systemoperating at 30% to 100% of the designed flow rate capacity of thesystem, or 30% to 100% of the TOC concentration of the target TOCconcentration of the inlet water, or 30% to 100% of the maximum amountor rate of addition of persulfate that can be added to the reactor. Thethird mode may be indicative of the system operating at greater than100% of the designed flow rate capacity of the system, or greater than100% of the TOC concentration of the target TOC concentration of theinlet water, or greater than 100% of the maximum amount or rate ofaddition of persulfate that can be added to the reactor.

TOC measurements can be made at one or more points along the flow pathof the water through the system, for example, system 100 or system 200.TOC measurements can be performed prior to addition of a precursorcompound to the actinic radiation reactor or to the water stream. Incertain embodiments TOC measurements are made on a water sample that hasbeen processed through a mixed bed ion exchange column so as to removeionic compounds from the water sample that may interfere with the TOCmeasurement. The mixed bed ion exchange column can comprise anionic andcationic resins that allow the transfer of ionic species from the wateronto the resin, thereby removing at least a portion of these speciesfrom the water. By removing the ionic species from the water, the TOCmeasurement can be performed more accurately. In particular examples,the mixed bed ion exchange column may be located downstream from areverse osmosis unit, and upstream of the actinic radiation reactor. Themixed bed ion exchange column may utilize USF™ NANO resin from SiemensWater Technologies Corp., Warrendale, Pa.

TOC measurements can also be made downstream of primary actinicradiation reactor 218 or downstream of secondary actinic radiationreactor 221.

In some aspects of the invention, measurement of a compound in the waterto be treated or being treated can be performed. This can involvemeasuring a characteristic of the water. The measurement can alsoinvolve converting a first species in the water to a target species, orchanging a characteristic of the water, and re-measuring thecharacteristic of the water. In certain examples, the target species canbe sulfate ions. The measurement of the compound can be performed downto levels, for example, of less than 1 ppm. In some examples, themeasurement of the compound can be performed down to levels of, forexample, less than 100 ppb, 1 ppb, or 0.5 ppb.

In certain embodiments, the measurement of a compound in the water caninvolve measuring a first conductivity of the water or liquid stream,irradiating at least a portion of the water or liquid stream, measuringa second conductivity of the water or liquid stream after irradiating,and calculating a concentration of the compound based at least in parton the first conductivity measurement and the second conductivitymeasurement. The compound that is measured can be persulfate.Irradiating the water or liquid stream can comprise converting at leasta portion of the compound comprising persulfate into sulfate ions. Thecompound that is measured can also be a reducing agent such as sulfurdioxide. Irradiating the water or liquid stream can comprise convertingat least a portion of the compound comprising sulfur dioxide to sulfateions. The measurement of the compound in the water can be performed onthe water stream being treated, for example, in system 100 or system200, or can be performed on a side stream of the water being treated insystem 100 or system 200.

As shown in FIG. 2, using sensor 207, a measurement of the amount of acompound in the water or liquid stream can be provided by, for example,concentration or conductivity measurements. In some embodiments of theinvention, a first conductivity of the water stream output of vessel 220can be measured. This water stream can be irradiated by ultravioletlight, and a second conductivity of the water stream can be measured. Bycomparing the first conductivity measurement to the second conductivitymeasurement, a concentration or amount of persulfate in the water streamcan be determined. In some embodiments, a catalyst may be used insteadof utilizing ultraviolet light.

Similarly, using sensor 208, a measurement of the amount of reducingagent in the water or liquid stream can be provided. A firstconductivity of the water stream downstream from point of addition 230of reducing agent from the source of reducing agent 224 can be measuredusing sensor 208. This water stream can be irradiated by ultravioletlight, and then a second conductivity of the water stream can bemeasured. By comparing the first conductivity measurement to the secondconductivity measurement, a concentration or amount of reducing agent inthe water stream can be determined. In some embodiments, a catalyst maybe used instead of utilizing ultraviolet light.

Conductivity measurements may be used to determine oxidizing agentconcentration or reducing agent concentration because the liquid streamexiting the advanced oxidation process may be pure enough that othercontaminants in the stream do not contribute significantly as a sourceof noise to the measured changes in conductivity of the stream as it isirradiated by ultraviolet light from the sensor. For example the liquidstream may be from a source of ultrapure water such that it may be knownto, or may typically comprise very low or untraceable concentrations ofcontaminants other than what is desired to be measured, for example itmay be known to, or may typically, comprise a concentration of oxidizingagent or reducing agent, and very low or untraceable concentration ofother contaminants, that would allow for accurate measurements ofoxidizing agent or reducing agent. A stream having a resistivity ofgreater than 15 megaohm-cm is of sufficient purity to allow for anaccurate oxidizing or reducing agent concentration measurement.Furthermore, a stream having a resistivity of greater than 1 megaohm-cm,of greater than 5 megaohm-cm, or of of greater than 10 megaohm-cm is ofsufficient purity to allow for an accurate oxidizing or reducing agentconcentration measurement. However, there can be waters with a higherconductivity/lower resistivity that do not interfere with theconductivity change as it goes through the UV, for example NaCl. Wherethere are known contaminates such as residual TOC, the impact in thechange in the conductivity as it goes through the analyzer can beallowed for to provide an accurate oxidizing or reducing agentmeasurement.

In certain embodiments, it is desired to reduce or neutralize residualpersulfate in the irradiated water that exits the actinic radiationreactor to a target level. This may be achieved by including additionalultraviolet lamps or actinic radiation lamps downstream from the primaryactinic radiation reactor, which can help reduce the residual persulfateand reduce TOC. For example, FIG. 2 includes secondary actinic radiationreactor 221 which can be added to help reduce the residual persulfateand reduce the TOC in the water.

Techniques such as utilizing catalysts or reducing agents can be used toreduce or neutralize the residual persulfate in the water stream thatmay be present after processing through a primary actinic radiationreactor, and in some embodiments, after processing through a secondaryactinic radiation reactor. Reducing agents may include bisulfites andsulfur dioxide. The reducing agent can be added to the water streambased on the persulfate and reducing agent measurements, or othercharacteristics or properties of the system. The rate of addition can beadjusted during the process as the needs of the system change.

For example, the rate of addition of reducing agent based in part on thecalculated oxidizing agent concentration and the calculated reducingagent concentration.

One embodiment of the invention utilizing sensor 207 and sensor 208 isshown in FIG. 5. A water stream 520 which may be an output from aprimary actinic radiation reactor or a secondary radiation reactor maybe measured with sensor 507. Sensor 507 can measure a first conductivityof water stream 520. This water stream can then be irradiated byultraviolet light, and a second conductivity of water stream 520 can bemeasured. Using controller 532, a concentration or amount of persulfatein the water stream can be determined by comparing the firstconductivity measurement to the second conductivity measurement.

Similarly, using sensor 508, a measurement of the amount of reducingagent, such as sulfur dioxide, in water or liquid stream 526 can beprovided. A first conductivity of water stream 526, which is downstreamfrom point of addition 530 of reducing agent can be measured usingsensor 508. The sensor can irradiate water stream 526 with ultravioletlight, and then a second conductivity of water stream 526 can bemeasured. Using controller 532, a concentration or amount of reducingagent in the water stream can be determined by comparing the firstconductivity measurement to the second conductivity measurement.

At least one of the calculated concentration or amount of persulfate andthe calculated concentration or amount of reducing agent in water stream520 and water stream 526 can be utilized by controller 532 to controlthe rate or amount of reducing agent added to water stream 522. Incertain embodiments of the invention, the rate or amount of reducingagent is controlled to provide a minimum amount of reducing agent basedon the calculated concentration of persulfate measured using sensor 507.The rate or amount of reducing agent can also be controlled to provide aminimum amount of reducing agent based on the calculated concentrationof reducing agent measured using sensor 508.

In certain embodiments, the persulfate (S₂O₈) concentration, for examplein stream 222 or 522, can be calculated based on the following formula:S₂O₈ (ppb)=[conductivity cell 2(μS)−conductivity cell 1(μS)]×γ,wherein γ is a constant determined based on, for example, theconductivity of sulfate and the conductivity of persulfate.

Although FIG. 5 is illustrated with each of sensor 507 and sensor 508comprising two conductivity cells, it can be envisioned that each ofsensor 507 and sensor 508 can comprise one conductivity cell in which afirst conductivity of a water sample is measured, irradiation of thewater sample occurs, and a second conductivity of the water sample ismeasured. The above equation can be used to determine the persulfateconcentration, wherein ‘conductivity cell 2’ represents the secondmeasured conductivity of the water, and ‘conductivity cell 1’ representsthe first measured conductivity of the water.

An embodiment of the disclosure wherein each of the oxidizing agentconcentration sensor and the reducing agent concentration sensorcomprises a single conductivity cell is shown in FIG. 14. The oxidizingagent concentration sensor 707 may comprise an oxidizing agentconductivity cell and a source of ultraviolet light. The reducing agentconcentration sensor 708 may comprise a reducing agent conductivity celland a source of ultraviolet light. In some embodiments, persulfate maybe the oxidizing agent and sulfur dioxide the reducing agent.Alternatively, sulfur dioxide may be the oxidizing agent. Alternatively,various bisulfates may be the reducing agent. The concentration ofpersulfate in stream 720, where persulfate is the oxidizing agent may becalculated through use of the following formula:S₂O₈ (ppb)=[conductivity cell post-uv(μS)−conductivity cellpre-uv(μS)]×γ,wherein γ is a constant determined based on, for example, theconductivity of persulfate. Stream 720 may be a stream from an upstreamprocess, for example, an advanced oxidation process, an actinicradiation reactor, a semiconductor manufacturing facility, or anothersource. The stream may be an ultrapure water stream in which othercontaminants are present in very low or untraceable concentrations so asto not interfere with the measurement of persulfate. Fluid from stream720 may enter the sensor 707, where the single conductivity cellmeasures the conductivity of the stream prior to irradiation from asource of ultraviolet light (“pre-uv”). This measures the conductivityof the stream prior to providing ultraviolet light to the conductivitycell from the source of ultraviolet light. For example, this may measurethe conductivity of a sample of the stream prior to providingultraviolet light to the conductivity cell from the source ofultraviolet light. The fluid may then be subjected to irradiation fromthe source of ultraviolet light and the single conductivity cell maysubsequently measure conductivity of the irradiated fluid subsequent toirradiation (“post-uv”). This measures the conductivity of the streamafter providing ultraviolet light to the conductivity cell from thesource of ultraviolet light. For example, this may measure theconductivity of the sample of the stream after providing ultravioletlight to the conductivity cell from the source of ultraviolet light.

A similar process may be used to calculate the sulfur dioxideconcentration (if sulfur dioxide is being used as the reducing agent),based on measurements of a single conductivity cell in sensor 708.

The concentration of sulfur dioxide in stream 726, where sulfur dioxideis the reducing agent, may be calculated through use of the followingformula:SO₂ (ppb)=[conductivity cell post-uv(μS)−conductivity cellpre-uv(μS)]×γ,wherein γ is a constant determined based on, for example, theconductivity of sulfur dioxide.

Fluid from a reduced liquid stream 726, which may be downstream of thereducing agent introduction point 730 where a source of reducing agentis disposed to introduce the reducing agent to the liquid streamdownstream 722 of the oxidizing agent concentration sensor 707, mayenter the sensor 708, where the single conductivity cell measures theconductivity of the reduced stream prior to irradiation from a source ofultraviolet light. The reduced fluid may then be subjected toirradiation from the source of ultraviolet light to provide anirradiated reduced liquid stream and the single conductivity cell maysubsequently measure conductivity of the irradiated reduced liquidstream subsequent to irradiation produced by providing ultraviolet lightto the conductivity cell from the source of ultraviolet light. While aseparate ultraviolet light source is used for each of the sensors 707and 708 shown in the embodiment depicted in FIG. 14, it should beunderstood that the system may also be configured so that a singleultraviolet light source is used to provide light to each of the twosensors 707 and 708.

The controller 732 may use the calculated oxidizing agent concentrationand reducing agent concentration to determine, in part, the amount ofreducing agent to introduce into a reduced liquid stream 726. Thecontroller 732 may be configured to generate a control signal thatregulates introduction of the reducing agent, either its rate ofaddition or an amount of addition, based in part on an input signal orseries of input signals from one of the oxidizing agent concentrationsensor 707 and the reducing agent concentration sensor 708. Thecontroller 732 may be configured to generate a control signal based inpart on the calculations of the oxidizing agent concentration and thereducing agent concentration. The controller 732 may be configured togenerate the control signal based on at least one of a first inputsignal from the oxidizing agent conductivity cell prior to irradiationfrom the first source of ultraviolet light and a second input signalfrom the oxidizing agent conductivity cell subsequent to irradiationfrom the first source of ultraviolet light. the controller is furtherconfigured to generate the control signal based on at least one of athird input signal from the reducing agent conductivity cell prior toirradiation from the second source of ultraviolet light and a fourthinput signal from the reducing agent conductivity cell subsequent toirradiation from the second source of ultraviolet light. The controller732 may be further configured to generate the control signal based on atleast one of a third input signal from the reducing agent conductivitycell prior to irradiation from the second source of ultraviolet lightand a fourth input signal from the reducing agent conductivity cellsubsequent to irradiation from the second source of ultraviolet light.

An alternative embodiment of the disclosure implementing a single sensorcomprising a single conductivity cell is shown in FIG. 15. Persulfatemay be the oxidizing agent and sulfur dioxide the reducing agent.Alternatively, sulfur dioxide may be the oxidizing agent. Alternatively,various bisulfates may be the reducing agent.

Stream 820 may be a stream from an upstream process, for example, anadvanced oxidation process, an actinic radiation reactor, asemiconductor manufacturing facility, a reverse osmosis device, oranother source. A portion 824 of the fluid from stream 820 may enter thesensor 807, where the single conductivity cell measures the conductivityof the stream prior to irradiation from an ultraviolet light source. Thefluid may then be subjected to ultraviolet light irradiation from theultraviolet light source to provide an irradiated liquid stream and thesingle conductivity cell may measure the conductivity of the irradiatedliquid stream subsequent to irradiation.

The portion 824 may then be directed out of the sensor through a pipe ora series of pipes (not shown in FIG. 15). The measured portion 824 mayeither be directed to a drain or it may be returned to flow line 820 or826.

A similar process may be used to calculate the sulfur dioxideconcentration, based on measurements of a single conductivity cell insensor 807. A portion 834 of fluid from a reduced stream 826, which maybe downstream of the sulfur dioxide introduction point 830, enters thesensor 807, where the single conductivity cell measures the conductivityof the stream prior to irradiation from an ultraviolet light source. Thefluid may then be subjected to ultraviolet light irradiation from theultraviolet light source to provide an irradiated reduced liquid streamand the single conductivity cell may measure the conductivity of thefluid subsequent to irradiation.

The concentration sensor 807 may then be emptied of the measured portion834 using the piping and valve arrangement described above in relationto measured portion 824. In this manner, a single sensor 807 may be usedto alternate between taking persulfate concentration measurements andsulfur dioxide concentration measurements.

The controller 832 may use the calculated concentrations oxidizing agentconcentration and reducing agent concentration to determine, in part,the amount of reducing agent to introduce at the point of addition 830to the system as part of stream 826.

The controller 832 may be configured to generate a control signal thatregulates introduction of sulfur dioxide, for example, its rate ofaddition or an amount of addition, to a liquid stream 820 to produce areduced liquid stream 826, based in part on the calculations of thepersulfate concentration and the sulfur dioxide concentration, in thecase where persulfate is the oxidizing agent and sulfur dioxide thereducing agent.

In some circumstances, it may not be necessary to introduce a reducingagent to the stream downstream of the actinic radiation reactor.Accordingly, an alternative embodiment of the system comprises only asingle sensor having a single conductivity cell, where the sensor isconfigured to measure an oxidizing agent (for example, persulfate)concentration of the stream, or a portion of the stream, exiting theactinic radiation reactor.

In other embodiments, the reducing agent may be added to the stream, butit may not be necessary to measure the concentration of reducing agentin the stream. In this embodiment, the persulfate concentration may ormay not be measured using sensor 807.

Systems 100 and 200 can further comprise one or more control systems orcontrollers 105 and 232. Control systems 105 and 232 are typicallyconnected to one or more sensors or input devices configured anddisposed to provide an indication or representation of at least oneproperty, characteristic, state or condition of at least one of aprocess stream, a component, or a subsystem of treatment systems 100 and200. For example, control system 105 can be operatively coupled toreceive input signals from any one or more of source 110 and sensors106, 107, and 108. Control system 232 can be operatively coupled toreceive input signals from any one or more of source 210 and sensors206, 207, 208, and 209. The input signals can be representative of anyintensive property or any extensive property of the water from source110, or water stream in the system. For example, input signals can berepresentative of any intensive property or any extensive property ofthe treated ultrapure water from ion exchange column 140L, and ionexchange column 140P of FIG. 1. The input signals can also berepresentative of any intensive property or any extensive property ofthe treated ultrapure water from reverse osmosis unit 212, secondaryactinic radiation reactor 220, or after point of addition of reducingagent 230. For example, one or more input signals from source 110 orsource 210 can provide an indication of the resistivity or conductivity,the flow rate, the TOC value, the temperature, the pressure, theconcentration of metals, the level or amount of bacteria, the dissolvedoxygen content, and/or the dissolved nitrogen content of the inlet ormake-up water. Input devices or sensors 106, 107 and 108, and 206, 207,208, and 209 may likewise provide any one or more such representationsof the at least partially treated water through system 100 or system200. In particular, any one of the sensors can provide an indication ofthe temperature, conductivity, or concentration of a particular compoundor species in the at least partially treated water or ultrapure water.Although only sensors 106, 107, and 108 and 206, 207, 208, and 209 areparticularly depicted, additional sensors may be utilized including, forexample, one or more temperature, conductivity or resistivity sensors insystems 100 and 200.

Control systems 105 and 232 can be configured to receive any one or moreinput signals and generate one or more drive, output, and controlsignals to any one or more unit operations or subsystems of treatmentsystems 100 and 200. As illustrated, control systems 105 and 232 can,for example, receive an indication of a flow rate, a TOC level, or both,of water from source 110 and/or 210, or from another position within thesystem. Control systems 105 and 232 can then generate and transmit adrive signal to source 122 or source 216 of precursor compound to, ifnecessary, adjust the rate of addition of the precursor compoundintroduced into the water stream entering reactor 120 or reactor 218. Inone embodiment, control system 232 can, for example, receive anindication of a concentration of a particular compound or species in thewater from sensor 207 and sensor 208. Control system 232 can thengenerate and transmit a drive signal to source 224 of reducing agent to,if necessary, adjust the rate of addition of the reducing agentintroduced into the water stream at point of addition 230. The drivesignal is typically based on the one or more input signals and a targetor predetermined value or set-point. For example, if the input signalthat provides a representation of the TOC value of the inlet water fromsource 110 or source 210 is above the target TOC value or a range ofacceptable TOC value, i.e., a tolerance range, then the drive signal canbe generated to increase an amount or a rate of addition of theprecursor compound from source 122 or source 216. The particular targetvalues are typically field-selected and may vary from installation toinstallation and be dependent on downstream, point of use requirements.This configuration inventively avoids providing water having undesirablecharacteristics by proactively addressing removal of contaminants andalso avoids compensating for the system's residence or lag responsetime, which can be a result of water flowing through the system and/orthe time required for analysis.

In some embodiments, control systems 105 and 232 can, for example,receive an indication of a flow rate, a TOC concentration or level,and/or a persulfate amount or rate of addition, and generate andtransmit a drive signal to reactor 120 or reactor 218 or 220, or morespecifically to the lamps of the reactor to adjust or modify at leastone of the one or more lamps in operation and the intensity of thelamps. The drive signal can be based on the one or more input signalsand a target or predetermined value or set-point, or threshold value.For example, if the input signal that provides a representation of theTOC value of the inlet water from source 110 or source 210 is above thetarget TOC value or threshold value, or a range of acceptable TOC value,i.e., a tolerance range, then the drive signal can be generated toadjust the operating mode of the reactor by adjusting at least one ofthe lamp configuration and the lamp intensity.

Control systems 105 and 232 may further generate and transmit additionalcontrol signals to, for example, energize or adjust an intensity orpower of output radiation emitted by at least one radiation source inreactor 120, 218, or 220. Thus, depending on the amount or rate ofaddition of the precursor compound, or on the level of TOC in the waterstream entering the reactors, the control signal may be increased ordecreased appropriately, incrementally or proportionally. This featureserves to prolong service life of the one or more radiation sources andreduce energy consumption.

Control systems 105 and 232 may also be configured in feedbackarrangement and generate and transmit one or more control signals to anyone or both of the precursor compound source 122 and 214, and reactors120, 218, and 220, and reducing agent source 224. For example, the TOCvalue or the resistivity, or both, of the ultrapure product water indistribution system 103, or from the sensors 107 or 108, may be utilizedto generate control signals to any of source 122 and reactor 120.

During periods of high initial TOC fluctuations, the feed-forwardcontrol can be utilized to compensate for instrument delay. Thispreemptive approach injects the precursor compound, typically at asurplus relative to the amount of contaminants. During periods of stableTOC levels, the feedback approach may be utilized with or without thefeed-forward control.

Control system 105 may further generate and transmit a control signalthat adjusts a rate of heat transfer in chiller 130 based on, forexample, an input signal from sensors 107 or 108, or both. The controlsignal may increase or decrease the flow rate and/or the temperature ofthe cooling water introduced into chiller 130 to provide treated waterto distribution system 103 at a desired or predetermined temperature.

Control system 105 may further generate and transmit a control signalthat energizes pump 166 or adjust a flow rate of the at least partiallytreated water flowing therethrough. If the pump utilizes a variablefrequency drive, the control signal can be generated to appropriatelyadjust the pump motor activity level to achieve a target flow ratevalue. Alternatively, an actuation signal may actuate a valve thatregulates a rate of flow of the at least partially treated water frompump 166.

Control systems 105 and 232 of the invention may be implemented usingone or more processors as schematically represented in FIG. 6. Controlsystem 105 may be, for example, a general-purpose computer such as thosebased on an Intel PENTIUM®-type processor, a Motorola PowerPC®processor, a Sun UltraSPARC® processor, a Hewlett-Packard PA-RISC®processor, or any other type of processor or combinations thereof.Alternatively, the control system may include specially-programmed,special-purpose hardware, for example, an application-specificintegrated circuit (ASIC) or controllers intended for analyticalsystems.

Control systems 105 and 232 can include one or more processors 605typically connected to one or more memory devices 650, which cancomprise, for example, any one or more of a disk drive memory, a flashmemory device, a RAM memory device, or other device for storing data.Memory device 650 is typically used for storing programs and data duringoperation of the systems 100 and 200 and/or control systems 105 and 232.For example, memory device 650 may be used for storing historical datarelating to the parameters over a period of time, as well as operatingdata. Software, including programming code that implements embodimentsof the invention, can be stored on a computer readable and/or writeablenonvolatile recording medium, and then typically copied into memorydevice 650 wherein it can then be executed by processor 605. Suchprogramming code may be written in any of a plurality of programminglanguages, for example, Java, Visual Basic, C, C#, or C++, Fortran,Pascal, Eiffel, Basic, COBAL, or any of a variety of combinationsthereof.

Components of control system 105 and 232 may be coupled by aninterconnection mechanism 610, which may include one or more busses,e.g., between components that are integrated within a same device,and/or a network, e.g., between components that reside on separatediscrete devices. The interconnection mechanism typically enablescommunications, e.g., data, instructions, to be exchanged betweencomponents of the system.

Control systems 105 and 232 can also include one or more input devices620 receiving one or more input signals i₁, i₂, i₃, . . . i_(n), from,for example, a keyboard, mouse, trackball, microphone, touch screen, andone or more output devices 630, generating and transmitting, one or moreoutput, drive or control signals, s₁, s₂, s₃, . . . , s_(n), to forexample, a printing device, display screen, or speaker. In addition,control systems 105 and 232 may contain one or more interfaces 660 thatcan connect control systems 105 or 232 to a communication network (notshown) in addition or as an alternative to the network that may beformed by one or more of the components of the system.

According to one or more embodiments of the invention, the one or moreinput devices 620 may include components, such as but not limited to,valves, pumps, and sensors 106, 107, and 108, and 206, 207, 208, and 209that typically provide a measure, indication, or representation of oneor more conditions, parameters, or characteristics of one or morecomponents or process streams of systems 100 and 200. Alternatively, thesensors, the metering valves and/or pumps, or all of these componentsmay be connected to a communication network that is operatively coupledto control systems 105 and 232. For example, sensors 106, 107, and 108and 206, 207, 208, and 209 may be configured as input devices that aredirectly connected to control systems 105 and 232, metering valvesand/or pumps of subsystems 122 and 124 may be configured as outputdevices that are connected to control system 105, and any one or more ofthe above may be coupled to a computer system or an automated system, soas to communicate with control systems 105 and 232 over a communicationnetwork. Such a configuration permits one sensor to be located at asignificant distance from another sensor or allow any sensor to belocated at a significant distance from any subsystem and/or thecontroller, while still providing data therebetween.

Control systems 105 and 232 can comprise one or more storage media suchas a computer-readable and/or writeable nonvolatile recording medium inwhich signals can be stored that define a program or portions thereof tobe executed by, for example, one or more processors 605. The one or morestorage media may, for example, be or comprise a disk drive or flashmemory. In typical operation, processor 605 can cause data, such as codethat implements one or more embodiments of the invention, to be readfrom the one or more storage media into, for example, memory device 640that allows for faster access to the information by the one or moreprocessors than does the one or more media. Memory device 640 istypically a volatile, random access memory such as a dynamic randomaccess memory (DRAM) or static memory (SRAM) or other suitable devicesthat facilitates information transfer to and from processor 605.

Although control systems 105 and 232 is shown by way of example as onetype of computer system upon which various aspects of the invention maybe practiced, it should be appreciated that the invention is not limitedto being implemented in software, or on the computer system asexemplarily shown. Indeed, rather than being implemented on, forexample, a general purpose computer system, the control system, orcomponents or subsystems thereof, may be implemented as a dedicatedsystem or as a dedicated programmable logic controller (PLC) or in adistributed control system. Further, it should be appreciated that oneor more features or aspects of the invention may be implemented insoftware, hardware or firmware, or any combination thereof. For example,one or more segments of an algorithm executable by processor 605 can beperformed in separate computers, each of which can be in communicationthrough one or more networks.

System 100 can further comprise a subsystem 176 for sanitizing and/orremoving any residue, particulate or other material retained on thesurface of the membranes of filtration apparatus 172 and 174. Subsystem176 can comprise one or more heat exchangers and pumps that allowtemperature cycling of the membranes of apparatus 172 and 174.Temperature cycling can be controlled by control system 105 byalternately providing hot and cool water into any of apparatus 172 and174 to allow expansion and contraction of components thereof whichfacilitates removal of any retained materials. Although not illustrated,subsystem 176 may also be connected to any unit operation of system 100to also facilitate cleaning and hot water sanitization of such unitoperations.

EXAMPLES

The function and advantages of these and other embodiments of theinvention can be further understood from the examples below, whichillustrates the benefits and/or advantages of the one or more systemsand techniques of the invention but do not exemplify the full scope ofthe invention.

Example 1

This example describes a system utilizing the techniques of theinvention as substantially represented in the schematic illustration ofFIG. 1.

The system 100 is fluidly connected to a source 110 of inlet water andis designed to provide ultrapure water to a semiconductor fabricationunit having the respective quality and characteristics listed in Table1.

The source 122 of precursor compound utilizes a pump to provide ammoniumpersulfate.

The reactor 120 comprises three serially connected UV lamps (SCD-120)providing UV radiation at about 254 nm.

The chiller 130 is a plate and frame heat exchanger designed to reducethe water temperature by 3° C.

The lead ion exchange column 140L includes parallel beds of USF™ MEG PPQion exchange resin.

The particulate filter 150 is rated to retain particles greater than0.05 micron.

The degasifier 160 includes two membrane contactors in parallelconnected to a vacuum source 162 at 30 mm Hg.

The pump 166 utilizes a variable speed drive and rated to provide 35 gpmat 100 psig.

The polish ion exchange column 140P includes serially connected beds ofUSF™ MEG PPQ ion exchange resin.

The ultrafiltration apparatus utilizes OLT-5026G ultrafiltrationmembranes from Asahi Chemical Company.

The online sensors utilized are listed in Table 2.

TABLE 1 Property Inlet Water Quality Product Water Quality TOC as urea,ppb <1-15 <1 Resistivity, Megaohm cm 18.0 >18.0 Particles @ 0.05μ,counts <1,000 <100 per liter Dissolved oxygen, ppb <100 <1,000 Dissolvednitrogen, ppb <500 <1,000 Metals <1 ppb, each <1 ppt Na <2 ppt Silica,ppb <3 <0.75 (total) Temperature, ° C. ~24 22-23

TABLE 2 Instrument Manufacturer Model TOC, control GE AnalyticalInstruments SIEVERS 900 turbo TOC, control GE Analytical InstrumentsSIEVERS 900 TOC, ultrapure water GE Analytical Instruments SIEVERS 500RLTOC, ultrapure water GE Analytical Instruments SIEVERS 500RLe TOC,ultrapure water GE Analytical Instruments Checkpoint Sensor Particulatesensor Particle Measurement UDI 50 Systems Resistivity Mettler ToledoThornton Dissolved oxygen Hach Ultra ORBISPHERE 3621 Dissolved nitrogenHach Ultra ORBISPHERE 3621 Ozone Hach Ultra ORBISPHERE MOCA

FIG. 7 which presents the quality of the ultrapure water product showsthat water having the desired characteristic can be treated by thesystems and techniques of the invention (labeled as “LUPW”) and comparedto an existing water supply system (labeled as “polish”) as well as analternate apparatus (labeled as “Entegris”). As shown in FIG. 7, thesystems of the invention can maintain the low TOC levels even duringfluctuations in inlet water quality.

Example 2

This example describes a system utilizing the techniques of theinvention as substantially represented in the schematic illustration ofFIG. 2. In this example, no secondary actinic radiation reactor wasutilized, and no source of reducing agent 224 was utilized.

The system 200 is fluidly connectable to a source 210 of inlet water andis designed to provide ultrapure water to a semiconductor fabricationunit.

The source 216 of precursor compound provides ammonium persulfate towater stream 214.

The primary reactor 218 comprises a first set of three seriallyconnected actinic radiation reactors, that are positioned in parallelwith a second set of three serially connected actinic radiationreactors. Each reactor provides UV radiation in a range of about 185 nmto about 254 nm.

FIG. 8, which presents a plot of total organic carbon (TOC)concentration versus time, where inlet water quality upstream of reactor218 is shown by data points represented by the symbol ♦, and quality ofthe treated water is shown by data points represented by the symbol

. FIG. 8 shows that total organic carbon (TOC) levels can be reduced toapproximately 1 ppb or less

Because of the noise observed in the inlet water TOC as shown in FIG. 8,a mixed bed column which included an ultrapure water resin (USF™ NANOresin, Siemens Water Technologies Corp., Warrendale, Pa.) was addedupstream of the inlet water TOC concentration sensor and downstream of areverse osmosis membrane to remove ionic constituents that may have beenthe cause of the irregular measurements.

FIG. 9, which presents a plot of total organic carbon (TOC)concentration versus time shows that inlet water TOC measurements can bestabilized through use of a mixed bed column upstream of the TOCconcentration sensor. As shown in FIG. 9, the TOC levels can be reducedto approximately 1 ppb or less utilizing the systems and techniques ofthe invention, and the low TOC levels can be maintained duringfluctuations in inlet water quality. Again, inlet water quality upstreamof reactor 218 is shown by data points represented by the symbol ♦, andquality of the treated water downstream of reactor 218 is shown by datapoints represented by the symbol

. FIG. 9 demonstrates that high levels of control can be achieved evenwith high fluctuations of inlet TOC. For example, the quality of treatedwater remained at or below 1 ppb TOC during a high fluctuation in TOCbetween times of about 20:10 and 21:35 on Day 1, and between times ofabout 5:24 and 8:00 on Day 2.

Example 3

This example describes a system utilizing the techniques of theinvention as substantially represented in the schematic illustration ofFIG. 2, and described in Example 2.

FIGS. 10 and 11, which present plots of total organic carbon (TOC)concentration versus time shows that the inlet water TOC level can bereduced to approximately 3 ppb or less, and in almost all instances toless than 1 ppb or less, utilizing the systems and techniques of theinvention. FIG. 10 shows data regarding inlet water containing urea, andFIG. 11 shows data regarding inlet water containing isopropyl alcohol.In FIG. 10, the TOC concentration fluctuates throughout the time periodshown. It is apparent that the systems and techniques of this inventioncan treat water containing urea and consistently provide treated waterat low TOC concentrations. In FIG. 11, the TOC concentration spikessignificantly on Day 3. The systems and techniques of this invention cantreat the water containing isopropyl alcohol to provide water at low TOCconcentrations, and has the ability to manage the TOC concentrationspike to maintain the TOC concentration in the treated water at or below3 ppb. In this particular example, it would be possible to achieve lowerTOC concentrations of the treated water to, for example, less than 1ppb, through modifications of the system, for example, increasing thepumping capacity of the persulfate pum.

Example 4

This example describes a system utilizing the techniques of theinvention as substantially represented in the schematic illustration ofFIG. 2, and described in Examples 2 and 3.

Persulfate concentration measurements were made utilizing sensor 207which measures a first conductivity of the water stream, appliesultraviolet light to the water stream, and measures a secondconductivity of the water stream. The persulfate concentration wascalculated based on the following equation,S₂O₈ (ppb)=[conductivity cell 2(μS)−conductivity cell 1(μS)]×γ,wherein γ is a constant calculated based on the conductivity of sulfateand the conductivity of persulfate.

FIG. 12, which presents a plot of residual persulfate versus time. Asshown in FIG. 12, a measurable amount of persulfate was detected in thetreated water. To reduce the amount of residual persulfate in thetreated water stream and allow for additional TOC reduction, a secondaryactinic radiation reactor was added downstream of the primary actinicradiation reactor. The secondary reactor 221 comprises a first set oftwo serially connected actinic radiation reactors, that are positionedin parallel with three additional sets of two serially connected actinicradiation reactors. Each reactor provides UV radiation at about 185 nmto about 254 nm.

Additionally, sulfur dioxide was added to the stream to reduce orneutralize the residual persulfate in the treated water stream. A sulfurdioxide concentration sensor was also added to the system to measure andcontrol the amount of sulfur dioxide added to the system, as shown inFIG. 5. Sulfur dioxide measurements can be calculated utilizing the plotpresented in FIG. 13 sulfur dioxide concentration versus the change inconductivity between a first conductivity measurement and a secondconductivity measurement can be used to determine the amount of sulfurdioxide in a water stream.

Example 5

This example describes a system in accordance with an embodiment inwhich the persulfate concentration sensor comprises two conductivitycells, such as the system shown in FIG. 5.

In this example, a dynamic system in which the conductivity of thesystem rises and falls was tested. Measurements from conductivity cellswere processed and compared against known values to test the accuracy ofthe processed measurements. Sulfuric acid was injected into the systemat varied rates to provide the varied conductivity measurement. Nopersulfate was added to the system until near the end of the experiment,as shown by line 3 of FIG. 16. Processed conductivity measurementsprovided estimations of persulfate concentrations. As will be describedbelow, the results depicted in FIG. 16 exemplify difficulties that mayarise from a two-conductivity-cell sensor configuration.

FIG. 16 is a graph showing conductivity measurements in accordance withthis embodiment. The y-axis comprises conductivity values expressed inmicrosiemens/cm (μS/cm), while the x-axis comprises time. Lines 1through 3 are plotted according to the conductivity values on the lefty-axis. Line 4 is plotted according to the conductivity values on theright y-axis.

Line 1 represents the measured delta conductivity. This value representsan estimation of the conductivity of the oxidant in the stream (forexample, persulfate or sulfur dioxide). It is arrived at by subtractingthe measured conductivity value at the second conductivity cell(subsequent to irradiation by an ultraviolet light source) by themeasured conductivity value at the first conductivity cell (prior toirradiation from an ultraviolet light source).

Line 2 represents the adjusted delta conductivity. This value representsan adjustment to the measured delta conductivity resulting from furtherprocessing of data in an effort to arrive at what is believed to be amore accurate representation of the conductivity of the stream for whichan oxidant, such as persulfate, is responsible.

Line 3 represents the known value of oxidant, for example, persulfate,in the system. The value is zero throughout most of the course of timerepresented in the graph, as no persulfate was present in the system,until a dose of persulfate, sufficient to contribute between 0.4 and 0.5μS to the conductivity of the stream, is injected near the end of theexperiment.

Line 4 represents the actual measured value of the first conductivitycell, in the two conductivity cell sensor system. The changes to thevalue of line 4 represent changing conductivity resulting from theaddition of sulfuric acid to the system. Sulfuric acid addition wasperformed to mimic dynamic shifts in the conductivity of the system thatmight result from, for example, a spike in TOC.

FIG. 16 shows lines 1 and 2 deviating from line 3 indicating that themeasured delta conductivity and adjusted delta conductivity struggle toaccurately represent the true value of persulfate in the system. Thedynamic changes in overall conductivity, represented by line 4 andcaused by intentional introduction of sulfuric acid to the system, arebelieved to interfere with the system's ability to accurately representthe persulfate value.

Notably, as the conductivity spikes from sulfuric acid dosing, themeasured and adjusted delta conductivities overcompensate, resulting innegative values. Likewise, where the sulfuric acid value drops, forexample at the middle of FIG. 16, the measured and adjusted deltaconductivities may spike, again, overcompensating. At other times themeasured and adjusted delta conductivities diverge in reaction tochanges in overall conductivity, for example on the right side of FIG.16. Where the overall conductivity is relatively stable (as representedby line 4) but oxidant is injected (as represented by line 3), measuredand adjusted delta conductivity are able to accurately measure thechanges in persulfate.

FIG. 16 demonstrates that two cell sensor systems may struggle toaccurately portray the persulfate value in a dynamic system, such as onewhere spikes in TOC are taking place. One possible cause for this is thedifficulty with properly aligning the two conductivity cells. Forexample, in a system where the persulfate sensor comprises two cells, acell prior to ultraviolet irradiation, and a cell after ultravioletirradiation, a time differential adjustment may be employed on thesecond cell in an effort to match its readings to the earlier readingsof the first sensor on the same portion of the stream. In a dynamicsystem where TOC levels, for example, are fluctuating, a small error inthe time delay may interfere with the accuracy of the persulfatereading.

Example 6

This example describes a system in accordance with an embodiment inwhich a high TOC event occurred. FIG. 17 is a graph showing conductivitymeasurements in accordance with this embodiment.

The y-axis comprises conductivity values expressed in microsiemens/cm(μS/cm), while the x-axis comprises time. Lines 1 through 4 are plottedaccording to the conductivity values on the left y-axis. Line 5 isplotted according to the conductivity values on the right y-axis.

Lines 1-5 represent data from five analyzers in parallel. Lines 1-4represent adjusted delta conductivity values for persulfate in fourparallel side streams. Lines 1 and 2 present data from parallel sensorscomprising two conductivity cells, each. Lines 3 and 4 present data fromparallel sensors comprising one conductivity cell, each. Line 5represents the measured conductivity of the feed water mainline, whichmay be, for example, effluent from an advanced oxidation process.

As discussed above, when a TOC spike occurs in the system, the adjusteddelta conductivity provided by a two-cell sensor may fail to depict theevent accurately. Line 5 in FIG. 17 depicts such a TOC spike along withan accompanying conductivity change at about time, 19:12. In the case ofFIG. 17, the adjusted delta conductivity depicted in lines 1 and 2 oftwo parallel two-cell sensors, first presented too high of a value,followed by too low of a value. As discussed above with respect to FIG.16, alignment issues between the first conductivity cell and the secondconductivity cell are believed to be a cause for the inaccurate oxidantreadings.

Lines 3 and 4 represent data from two parallel single cell sensors inwhich the sample is processed in a batch process by capturing a samplein a sensor with the ultraviolet light turned off to obtain the initialconductivity reading. The ultraviolet light is then turned on to processthe sample converting either persulfate or sulfur dioxide to sulfuricacid to allow an concentration of residual chemical to be calculated.Since a batch process with a single cell is used, there is nomisalignment of the pre-UV and post-UV reading that could result inover-compensating readings (excessively high or negative). The use ofthe single-cell sensor may, therefore, result in a more accurateanalysis.

Example 7

This example describes a system in accordance with an embodiment inwhich the persulfate concentration sensor comprises only oneconductivity cell and the sulfur dioxide sensor comprises only oneconductivity cell, such as the system shown in FIG. 14.

FIG. 18 is a graph showing conductivity measurements in accordance withthis embodiment.

The y-axis comprises conductivity values expressed in microsiemens/cm(μS/cm), while the x-axis comprises time. Lines 1 and 2 represent deltaconductivity values processed from measurements taken by two parallelpersulfate sensors each having a single conductivity cell. Lines 3 and 4represent delta conductivity values processed from measurements taken bytwo parallel sulfur dioxide sensors each having a single conductivitycell.

The data on the graph of FIG. 18 show a system acting as desired. Wherea spike in persulfate occurs (lines 1 and 2), a corresponding spike inthe reducing agent, for example, sulfur dioxide (lines 3 and 4), isprovided. The initial sulfur dioxide spike occurs in anticipation of theelevated persulfate. During the elevated sulfur dioxide feed, the impactof the persulfate elevation is seen by the interim dip in the sulfurdioxide. The added sulfur dioxide removes the excess persulfate, and thepersulfate residual returns to baseline values.

The improved performance over the system represented in FIGS. 16 and 17indicates certain advantages that may exist in embodiments in which thesensor comprises a single conductivity cell. This may be due toavoidance of issues related to conductivity cell alignment.

Having now described some illustrative embodiments of the invention, itshould be apparent to those skilled in the art that the foregoing ismerely illustrative and not limiting, having been presented by way ofexample only. Numerous modifications and other embodiments are withinthe scope of one of ordinary skill in the art and are contemplated asfalling within the scope of the invention. In particular, although manyof the examples presented herein involve specific combinations of methodacts or system elements, it should be understood that those acts andthose elements may be combined in other ways to accomplish the sameobjectives.

Those skilled in the art should appreciate that the parameters andconfigurations described herein are exemplary and that actual parametersand/or configurations will depend on the specific application in whichthe systems and techniques of the invention are used. Those skilled inthe art should also recognize or be able to ascertain, using no morethan routine experimentation, equivalents to the specific embodiments ofthe invention. It is therefore to be understood that the embodimentsdescribed herein are presented by way of example only and that, withinthe scope of the appended claims and equivalents thereto; the inventionmay be practiced otherwise than as specifically described.

Moreover, it should also be appreciated that the invention is directedto each feature, system, subsystem, or technique described herein andany combination of two or more features, systems, subsystems, ortechniques described herein and any combination of two or more features,systems, subsystems, and/or methods, if such features, systems,subsystems, and techniques are not mutually inconsistent, is consideredto be within the scope of the invention as embodied in the claims.Further, acts, elements, and features discussed only in connection withone embodiment are not intended to be excluded from a similar role inother embodiments.

As used herein, the term “plurality” refers to two or more items orcomponents. The terms “comprising,” “including,” “carrying,” “having,”“containing,” and “involving,” whether in the written description or theclaims and the like, are open-ended terms, i.e., to mean “including butnot limited to.” Thus, the use of such terms is meant to encompass theitems listed thereafter, and equivalents thereof, as well as additionalitems. Only the transitional phrases “consisting of” and “consistingessentially of,” are closed or semi-closed transitional phrases,respectively, with respect to the claims. Use of ordinal terms such as“first,” “second,” “third,” and the like in the claims to modify a claimelement does not by itself connote any priority, precedence, or order ofone claim element over another or the temporal order in which acts of amethod are performed, but are used merely as labels to distinguish oneclaim element having a certain name from another element having a samename (but for use of the ordinal term) to distinguish the claimelements.

What is claimed is:
 1. A method for controlling introduction of areducing agent to a liquid stream comprising: introducing an oxidizingagent to the liquid stream; measuring a first conductivity of the liquidstream in a conductivity cell of a first sensor; irradiating the liquidstream in the conductivity cell of the first sensor to provide anirradiated liquid stream; measuring a second conductivity of theirradiated liquid stream in the conductivity cell of the first sensor;calculating the oxidizing agent concentration of the liquid stream basedon the first conductivity measurement, the second conductivitymeasurement, and a constant based on the conductivity of the oxidizingagent; introducing a reducing agent to the liquid stream to provide areduced liquid stream; measuring a third conductivity of the reducedliquid stream in a conductivity cell of a second sensor; irradiating thereduced liquid stream in the conductivity cell of the second sensor toprovide an irradiated reduced liquid stream; measuring a fourthconductivity of the irradiated reduced liquid stream in the conductivitycell of the second sensor; calculating the reducing agent concentrationbased on the third conductivity measurement the fourth conductivitymeasurement, and a constant based on the conductivity of the reducingagent; and regulating at least one of a rate of addition and an amountof the reducing agent introduced to the liquid stream based on at leastone of the calculated oxidizing agent concentration and the calculatedreducing agent concentration.
 2. The method of claim 1, wherein theoxidizing agent comprises persulfate.
 3. The method of claim 2, whereinthe reducing agent comprises sulfur dioxide.
 4. The method of claim 1,wherein the liquid stream has a resistivity of at least about 15megaohm-cm.
 5. The method of claim 1, wherein the liquid stream upstreamof the first sensor has a resistivity of at least about 1 megaohm-cm. 6.A method for measuring an oxidizing agent concentration and a reducingagent concentration in a liquid stream having a resistivity of at leastabout 15 megaohm-cm, the method comprising: introducing an oxidizingagent to the liquid stream; measuring a first conductivity of the liquidstream in a conductivity cell of a first sensor; irradiating the liquidstream in the conductivity cell of the first sensor to provide anirradiated liquid stream; measuring a second conductivity of theirradiated liquid stream in the conductivity cell of the first sensor;calculating the oxidizing agent concentration of the liquid stream basedin part on the first conductivity measurement, and the secondconductivity measurement, and a constant based on the conductivity ofthe oxidizing agent; introducing a reducing agent to the liquid streamto provide a reduced liquid stream; measuring a third conductivity ofthe reduced liquid stream in a conductivity cell of a second sensor;irradiating the reduced liquid stream in the conductivity cell of thesecond sensor to provide an irradiated reduced liquid stream; measuringa fourth conductivity of the irradiated reduced liquid stream in theconductivity cell of the second sensor; and calculating the reducingagent concentration of the reduced liquid stream based on the thirdconductivity measurement, the fourth conductivity measurement, and aconstant based on the conductivity of the reducing agent.
 7. The methodof claim 6, wherein the oxidizing agent comprises persulfate.
 8. Themethod of claim 7, wherein the reducing agent comprises sulfur dioxide.9. A method for controlling introduction of a reducing agent to a liquidstream comprising: introducing an oxidizing agent to the liquid stream;introducing a portion of the liquid stream to a concentration sensorcomprising a single conductivity cell; measuring a conductivity of theportion of the liquid stream in the conductivity cell; irradiating theportion of the liquid stream in the conductivity cell to provide anirradiated liquid stream; measuring a conductivity of the irradiatedliquid stream in the conductivity cell; calculating an oxidizing agentconcentration of the liquid stream based on the conductivity of theportion of the liquid stream, the conductivity of the irradiated liquidstream, and a constant based on the conductivity of the reducing agent;introducing a reducing agent to the liquid stream to provide a reducedliquid stream; introducing a portion of the reduced liquid stream to theconcentration sensor; measuring a conductivity of the portion of thereduced liquid stream in the conductivity cell; irradiating the portionof the reduced liquid stream in the conductivity cell to provide anirradiated reduced liquid stream; measuring a conductivity of theirradiated liquid stream in the conductivity cell; calculating areducing agent concentration of the reduced liquid stream based on theconductivity of the portion of the reduced liquid stream, theconductivity of the irradiated reduced liquid stream, and a constantbased on the conductivity of the reducing agent; and regulatingintroduction of the reducing agent to the liquid stream based in part onthe oxidizing agent concentration and the reducing agent concentration.10. The method of claim 9, wherein the oxidizing agent concentrationcomprises persulfate concentration.
 11. The method of claim 10, whereinthe reducing agent comprises sulfur dioxide.
 12. The method of claim 9,wherein the liquid stream has a resistivity of at least about 15megaohm-cm.
 13. The system of claim 9, wherein the liquid streamupstream of the concentration sensor has a resistivity of at least about1 megaohm-cm.